Dry Rot 

IN 

Factory Timbers 



1915 



PRICE, 26 CENTS 



INSPECTION DEPARTMENT 

Associated Factory 
Mutual Fire Insurance Companies^ 

31 Milk Street, Boston, Mass. 



SPECIFICATIONS 

Suggested for a Special Grade of Longleaf Pine 
For Use in flutual Factories 



In making contracts for beams, columns and plank to be 
used in "Slow Burning Construction," the following specifica- 
tions are recommended for reasons given in the following 
pages. 

Density. No part of the material shall have a density of 
less than 30 pounds per cubic foot when tested by boring smooth 
holes one inch in diameter and two inches deep in the ends of the 
stick, drying to constant weight at 212° F. and weighing the 
borings and computing the density from the volume of the hole. 

Rosin. None of the heartwood shall show less than four 
per cent of rosin by weight when borings are taken with a one 
inch bit with a hole two inches deep, dried to constant weight 
at 212° P. and extracted with benzole, the extracted rosin 
evaporated until it is not soft or sticky when touched with the 
finger at 70° F. 

Heartwood. Heartwood shall show in all four faces of every 
stick, and sap wood shall not extend more than two inches from 
the comer at any place, measured perpendicularly to the corner 
across the face. 

Growth Rings. For timbers 6" x 8", or larger, there must 
show on the cross section between the third and fourth inch, 
measured radially from the heart center or pith, not less than 
six annual rings o^ growth, a majority of which shall show at 
least one-third. <5jLirimer wood, which is the dark portion of the 
annual rings; but.ti^ide ringed material excluded by this rule will 
be acceptable,' providing that in the majority of the annual 
rings the dark ring is hard and in width equal to or greater than 
the adjacent light colored ring. 

For pieces in which the center is not included, there must show 
on the cross section, an average of not less than six annual rings 
of growth, with not less than one-third summerwood. Timbers 
will be rejected in which there is no sharp contrast in color between 
the springwood and summerwood. 

Defects. No timber with knots greater than one inch in 
diameter, or rot, or injurious shakes will be accepted. 

Branding. Longleaf pine sold under this specification shall 
be branded with the letters "F. M.," the name of the lumber 
manufacturer, the location of the saw-mill from which it comes, 
and the date of sawing, in letters at least one inch high. 

Note. P'urther details are given on page 68. When resistance to decay is 
to be secured by chemical treatment, poorer timber can be used, sptcitications 
as to defects, densities, etc., being so written as to assure the required strength. 
See pages 76 to 82. Common timber with thorough chemical treatment can 
probably be bought at a lower price than the special grade described above 
and for inost ]iurp(i<i-s will bo equ;il!v serviceable. 



I 



INSPECTION DEPARTMENT 

OF THE 

Associated Factory 
Mntaal Fire Insnrance Companies, 

31 Milk Street, Boston, Mass. 



March 15, 1915. 



DRY ROT 

IN 

FACTORY TIMBERS. 



The interest of the Factory Mutual Insurance Com= 
panies in Dry Rot of Timbers is threefold. 

FIRST: They have for fifty years been sponsors for 
so=called slow burning or mill construction. The economy 
and integrity of this excellent type of building is threat= 
ened by the remarkable increase in the prevalence of dry 
rot during the past few years. 

SECOND: Wood infected by dry rot ignites more easily 
than sound wood and mill timbers with rotted ends fall 
more quickly under fire. 

THIRD: The officers and engineers of these companies 
believe that the dangers of dry rot can be largely elimi= 
nated, with the consequent saving of many thousands 
of dollars to Mutual members. 



No. 32. Copyright, 1915, by 

2d Edition. C. H. Phinney, Trustee. 

5000-3-15. 



BRIEF ABSTRACT OF FOLLOWING HUNDRED PAGES. 

1. Thirty cases of dry rot, of greater or less magnitude, have 
been brought to the attention of the Mutual Companies within 
the past three years. Several million feet of lumber were involved , 
and, in some of the worst cases the safety of important struc= 
tures was menaced. There were undoubtedly many other 
cases which have not been reported. The direct money loss to 
Mutual members from this source is undoubtedly many thousand 
dollars each year in addition to the increased fire and life hazard 
from loss of strength and greater combustibility of rotting 
structural timbers. 

2. The varieties of fungi causing this destruction of factories 
are apparently few, and, while their habits and requirements are 
not well known, it is evident that the supply of moisture and 
the temperature are important controlling factors. 

3. Each variety of timber has its own pecuHar fungus 
destroyers, and, as the number of varieties of timber practically 
available for mill construction is limited, the problem is somewhat 
further simplified and resolves itself into the selection of timber 
with the greatest natural resistance to fungi practically attainable, 
and seeing that this is dry and free from dangerous living 
fungi when placed in the structure. 

4. In most cases, it is well worth the cost to thoroughly 

heat the building by use of its heating system as soon as 
possible after it is completed. This will hasten the drying and 
kill surface growths of dangerous dry rot fungi. This may 
fill all requirements in buildings of dry occupancy. 

5. The moist atmosphere present in such processes of manu- 
facture as paper making and cotton weaving, introduces conditions 
which probably no variety of wood now practically obtainable 
can withstand continuously without having its natural resistance 
to fungi reinforced by artificial antiseptic treatment. 

6. Timber of uniformly high natural resistance to fungi is 
difficult, if not impossible, to obtain by grading methods now in 
general use. The dense resinous longleaf pine from the butts 
of trees, which has been used in the past, has proved satisfactory. 
The present supply of so-called "Commercial longleaf pine,*' 
comprising all varieties of Southern pine, (North Carolina, 
shortleaf, loblolly, and Cuban, mixed indiscriminately with 
true longleaf), is proving far less reliable than the supply of 



3 

former years, and thus far no standard specifications have 
been adopted by means of which the purchaser can assure 
himself of the reliabihty of the lumber delivered. 

7. The percentages of rosin and the density are undoubtedly 
valuable indices of durability and strength. The rosin test is 
somewhat cumbersome to apply and is not recognized by the 
lumber trade. The density is roughly covered in the "Growth 
ring" or "Grain band rule" recently adopted by several lumber 
associations. 

8. It is probable that a close observer, who has had con- 
siderable experience with Southern pine, could select resinous 
dense wood with considerable certainty, and it would doubtless 
be worth while for a large user of Southern pine to employ such 
a man as buyer at the saw-mills. This is done by some of the 
German lumber importing companies. It is, of course, neces= 
sary to pay a premium for such selected timber, but it 
is well worth it, as an unreliable wood in an important structure 
would be expensive even as a gift. This plan is impracticable with 
the small or occasional purchaser, and to such the only course 
that can be at present recommended is to buy heartwood 
timber, of which the density, as indicated by the grain 
bands, is sufficient to insure the required strength, and 
to give this a chemical treatment of sufficient antiseptic 
power to kill any latent fungi that it may contain and to protect 
the surface from later attack. 

9. The process of antiseptic treatment, which, from the small 
am.ount of experience thus far available, appears to be best 
adapted to use on mill timber, is to soak it for a week in a 
one per cent solution of corrosive sublimate dissolved in 
water. This has been done at the mills in several cases recently, 
the treatment, with good heartwood, costing about three dollars 
a thousand. Lumber already treated with corrosive subli- 
mate can be obtained commercially, at a reasonable price, 
where it is desired to avoid the inconvenience and delay 
necessary for treatment on the job. When such treated timber 
is used, care should be taken to thoroughly swab with corrosive 
sublimate solution all parts of the interior of the stick that are 
exposed by cutting after the treatment is applied. 



RECENT PROGRESS. 

Since the publication of the first edition of this pamphlet in 
December, 1913, considerable progress has been made towards 
assuring more reliable timber for mill construction. 

The problem divides itself into two parts: 

First, that of untreated timber, or the possibility of securing 
uniformly reliable timber at a permissible price, which possesses 
sufficient natural resistance so that unaided it can withstand 
fungus in the moist atmosphere found in many rooms in textile 
mills, or in paper mills. 

Second, that of timber treated antiseptically, or timber which 
can be had in suitable lengths and sizes, with sufficient strength 
for the required load, and which can be given the necessary 
resistance to fungus by chemical treatment. 

In the past, good quality longleaf pine has given satisfactory 
service without antiseptic treatment; but the present supply, 
which comprises much loblolly, shortleaf and poorer longleaf, 
is lacking in natural resistance. Therefore, in order to make 
sure of obtaining a grade of Southern pine which can be used 
safely without antiseptic treatment, the present system of 
grading must be revolutionized, and based upon those physi- 
cal and chemical properties which underlie strength and resist- 
ance to fungus rather than upon the vague botanical distinctions 
now in use. 

During the past year, on behalf of the Factory Mutuals, I 
have visited longleaf pine forests and saw-mills in Louisiana, 
Alabama and Mississippi. By request, I attended the annual 
meeting of the Yellow Pine Manufacturers Association in New 
Orleans in order to explain the requirements of so-called "mill 
construction." The statement of our case was received with 
great courtesy, and this organization showed its interest in the 
subject by voting to have research work, tending to conserve 
the good qualities of their lumber, carried on at the Missouri 
Botanical Gardens in St. Louis. The Association also has 
under consideration new grading rules for structural timber. 

The Forest Products Laboratory of the United States Depart- 
ment of Agriculture has become much interested. I accepted 
an invitation to visit the Laboratory at Madison, Wisconsin, 
ftnd discussed the problem, and two representatives of this 



Laboratory have recently visited some of our textile mills, to 
study the conditions under which dry rot occurs. It is under- 
stood that they have laid out a large amount of additional 
research work for the coming year. This is probably the only 
institution in the country which has suitable facilities for carry- 
ing out this work in the comprehensive manner that is required, 
and, finally, it probably will be upon the results of work to be 
done by their experts, on the causes of resistance to fungi, the 
habits of important wood destroying fungi, and preservative 
processes, that permanently useful specifications for structural 
timbers can best be based. 

The Committee on Grading Rules for Structural Timber, of 
the American Society for Testing Materials, has been enlarged 
and several subcommittees formed for the purpose of recon- 
sidering timber specifications. 

Several factories insured in the Mutuals have, at our sug- 
gestion, during the past season, soaked pine and spruce planks 
for roofs in a weak solution of corrosive sublimate, in tanks 
located in their own yards, and have found that this process 
of wood preserving is easily carried out and the cost small. 
Photographs are shown in Figures 67, 68 and 69 of some of 
this work in progress. Other mills, seeking immunity from 
quick decay of timbers, have used coal tar compounds, and 
in two or three cases corrosive sublimate dissolved in wood 
alcohol has been used when the time for treatment was limited, 
or the timber was already in place and therefore could not be 
soaked in a tank. In a few cases, as suggested in our pamphlet 
of December, 1913, to arrest decay already begun, the timbers 
have been more or less sterilized by temporarily raising 
the interior temperature of the factory by means of its 
own heating system. 



EXTENT OF THE DESTRUCTION. 

The loss to Mutual mills from rotting timber is many 
thousands of dollars a year. It is not possible to state the 
amount with even approximate accuracy. The following photo- 
graphs will convey some idea of the character and extent of the 
destruction in a few cases. 




Figure 1. Part of 239,000 feet of spruce roof plank and 

HEMLOCK floor BEAMS REMOVED FROM A MASSACHUSETTS 
COTTON FACTORY DUE TO ROTTING IN FROM TWO TO 
FOURTEEN YEARS. 




Figure 2. Oak columns and white pine floor beams 

REMOVED from AN ENTIRE FLOOR OF A FACTORY IN ONTARIO, 

Canada, and replaced by steel after twenty-five years 
OF service. Infection was apparently recently intro- 
duced IN new lumber used for a basement floor. 




Figures. SE^'EXTEEX 12"x16" Soctherx pine beams rotted 

AXD REMOVED AFTER TWO YEARS' SERVICE IX A COTTOX 
FACTORY IX COXXECTICUT. 




Figure 4. Part of 7oU 6 " x lb" beams removed from a xew 

FACTORY IX jMoXTREAL, AFTER OXLY THREE YEARS' SERVICE, 
because REXDERED UXSAFE by DECAY. 




Figure 5. An old paper mill with hemlock frame rotted 
so badly that it was abandoned, showing opening where 
floor has fallen. 




Figure 6. l^'iNcais found gkowinh; on underside of roof 
PLANK IN A New York canning factory. (Camera pointed 
vertically upward.) 




Figure 7. Tin clad fire door of white pine, badly rotted 
only three years after it was installed in a massachu- 
setts cotton factory. 




Figure 8. Hemlock beam, rotted and crushed under a light 

LOAD, after two YEARS' SERVICE IN A MOIST BASEMENT. ThE 
ADJACENT LONGLEAF PINE COLUMN IS STILL SERVICEABLE AFTER 
FOURTEEN YEARS. 



10 




Figure 9. Rotted column crushed in an Ohio paper mill. 
The timber is loblolly pine. The rotting was ap- 
parently STARTED BY THE TIMBER BEING SOAKED BY A 
FLOOD. 




Figure 10. Fungus growing on Southern pine roof planks 

AND BEAMS OF A CHICAGO STOREHOUSE. ThE BUILDING IS 
INFECTED THROUGHOUT. ThE FRAME IS BEING REINFORCED 
AND PART OF ONE FLOOR HAS BEEN REPLACED WITH CONCRETE. 

(Camera pointed vertically upward.) 



11 



DRY ROT AND FIRE HAZARD. 

Partly rotten wood ignites much more easily than 
sound wood. 

Dry rot in factory timbers is of importance not only from 
the cost of replacement and. the danger of collapse, but because 
it increases the fire hazard. The increased combustibility of 
rotted fence posts and stumps is familiar to many casual observ- 
ers. The collapse of the Gledhill Wall Paper Factory of New 
York, after a small fire,^ presented an illustration of this hazard. 




Figure 11. Shows ends of mill beams completely destroyed 
although the beams themselves are not deeply burned. 



1. Engineering News, VoL 62, 1909, page 620. 



12 




Figure 12. Shows two sections of 14" x 16" white pine 

BEAMS, WITH ROTTED CENTERS, WHICH WERE RECENTLY REMOVED 
FROM ONE OF THE OLDER COTTON MILLS. WhEN LIGHTED 
WITH A MATCH, THEY CONTINUED TO BURN UNTIL ALL OF THE 
ROTTED WOOD WAS CONSUMED. 




Figure 13. Floor beams described above after the ignited 
rot had burned away, the fire going out of itself when 
it reached the sound wood. 



13 

THE INCREASED COMBUSTIBILITY OF WOOD AF- 
FECTED BY DRY ROT. 

The ignition point of rotted wood has been shown to be lower 
than that of sound wood.^ 

Under favorable conditions, large pieces will ignite at a tem- 
perature of 290° F., or even lower. 

The Alutual Companies have no definite records of increased 
losses from this source, owing, doubtless, to the efficiency of the 
complete automatic fire protection in Mutual risks, by means of 
which the fire is ordinarily extinguished before the fire resistant 
qualities of the construction are severely tried. 



1. Henry B. Hill, Proceedings of the American Academy of Arts & Sciences, 
Vol. 22, 1886, page 482. 



14 

SUGGESTIONS FOR EXAMINING AN INFECTED MILL. 

In examining a mill affected with dry rot, it is especially de- 
sirable to determine how far the rot has extended, whether it 
is stiU alive and whether it is of a variety which goes into a rest- 
ing state and may, therefore, be revived at anytime when the 
conditions of moisture become favorable-; also, whether it is a 
variety which may be destroyed by moderate heating or drying. 

The extent of the rotting can generally be estimated approxi- 
mately by boring test holes into the beams and columns at fre- 
quent intervals. If the material is badly rotted, the chips 
brought out will be in the form of a brown powder or mud, ac- 
cording as the wood is dry or wet. Sometimes, where the rot 
has not progressed so far as to entirely destroy the structure of 
the wood, the chips are browner than the sound wood and 
more brittle. 

Hammering on the timber with the round end of a ma- 
chinist's hammer is also sometimes useful where the wood is in 
an advanced state of decay. In some cases, where this test has 
been applied, the outer shell of apparently sound beams has 
been broken through, showing the entire destruction of the 
interior. The rotting in roof planks is generally much worse 
above the beams than in the middle of the bay, and, in some 
cases, planks which appear sound on the exposed surface will be 
found rotted above the beams so that a knife blade can be 
pushed entirely through them. 

To determine whether the rot is still alive is frequently a 
more complicated matter. If it is growing vigorously on the sur- 
face of the wood, the fresh growth of lace-like plants is significant, 
but the more frequent condition is where the dry rot 
fungus is growing inside the wood with no outward 
manifestation. In this case, a strong indication of living 
fungus is the moist appearance of a freshly cut section. In 
some cases, moist spots will remain for several days on such a 
section when left in a comparatively dry room. The only 
positive test, however, is to cut a large number of blocks 
about 2^" cube from the wood at the point where the rot 
just ceases to be apparent by the brown color, so that a part 
of each block is brown and a part of it has the appearance of 
sound wood. These should be placed in fruit jars and soaked in 
water containing 2% of citric or tartaric acid for about six 



15 



hours, then the water should be poured off and the jars covered and 
left at a temperature of about 75° F. for two or three weeks. If 
long threadlike growths, such as those shown in Figure 14, appear 
on any specimens, the fungus is doubtless alive and of a suspicious 
variety. Microscopic molds of various colors not infrequently 
appear on such cultures, but they do not indicate a wood destroy- 
ing fungus. 




Figure 14. Sterile rot plants as commonly seen. These 

PLANTS were cultivated ON SMALL BLOCKS IN FRUIT JARS. 

Scale one-half natural size. 



The culture blocks will not only show fungus in active 
growth, but also living fungus in a resting state. This is 
the only sure way in which fungus in this treacherous state can 
be discovered. Microscopic examination of sections w^ould show 
w^hether they contained the bulb-like formations indicating the 
resting state, but would not show whether, or not, they were alive. 
It is very rare indeed that fruiting plants, whether of the dry rot 
or other varieties, are found on structural timbers above the base- 
ment. Therefore, spores, the normal reproductive body, are prob- 
ably not common causes of perpetuating the disease in factories. 
Such fruiting plants are moreover very easily seen and identi- 
fied unless they are growing inside of hollow partitions or in 
concealed basements, as sometimes occurs. 

Some kinds of dry rot fungi can sometimes be arrested 
by heating, while, with some other varieties, this is not effective. 
Where there are no fruiting plants, the only practicable course is 
to judge, from the location of the rotted lumber, the probable 



16 

sensitiveness to heat, of the fungus causing the destruction. 
For example, a rotted roof plank in a paper mill or weaving 
mill, with the normal temperature from 80° F. to 100° F. at 
the roof, and frequently in summer higher than this, would not 
be expected to contain a variety of fungus which could be killed 
by heating to 115° F., while with rot discovered in the beams or 
columns of a moderately dry mill, with an average temperature of 
70° to 80°, heating would be worth a trial without further 
evidence as to the exact variety of fungus present. If fruiting 
plants are found, the plan of procedure may be somewhat 
simplified. 



17 



HOW WOOD ROTS. 

Rot in wood was originally supposed to be a chemical action 
similar to rusting of iron, and the delicate lace-like plants, tough 
brackets, or brown leathery groT^i:hs, were supposed to be at- 
tracted by the decayed wood rather than being the cause of the 
rotting. About 1870, it was shown by Hartig and others in 
Europe that fungi were the cause of rot instead of a result of it. 
The chemistry of the rotting process is not well known at the 
present time. It is probable that, there is some chemical action 
in addition to the life progress of the fungus through the wood 
cells. It is noted in blocks of sound wood, in which fungus has 
been cultivated, that when the fungus is freshly removed 
from the moist wood, it has the appearance of being 
bright and sound as ever ; but, after being left in a dry 
atmosphere for a time, the wood shrinks and forms the charac- 
teristic brown, cracked, and powdery material which is familiar 
as rotted wood. 

Without doubt, the fungus ceases to make any vital progress 
very soon after the drying commences, and the final browning 
and powdering is brought about by oxidation by the air, assisted 
by certain organic enzymes, either already present in the wood 
cells or formed by the activity of the fungus. A phenomenon 
which supports this theory is that the plants of certain wood 
destroying fungi when folded in a piece of white paper discolor 
it, changing it to a brown substance, probably an oxy- cellulose, 
leaving a fairly w^ell defined impression of themselves upon the 
paper. The}" will also form a developable image on a photo- 
graphic plate in the dark. 

It is customary in many lumber yards, particularly where 
Southern pine lumber is sold, to pass the planks and timber 
through a planer immediately before delivery. This not only 
smooths the material, but removes all fungus plants and leaves 
a bright surface which can be easily mistaken for sound 
wood, if it is used before drying has brought out the brown 
spots which are recognized as rotten wood. 



18 

NAMES OF THE COMMON TIMBER-DESTROYING 
FUNGI. 

There are but few common or popular names for fungi, 

and the few there are, such as dry rot, punk, toadstools, etc., 
are exceedingly vague and indefinite. The Latin names are 
commonly used in scientific literature. Their use implies an 
exact identification. 

In this pamphlet, the words "dry rot'* are used to signify 
broadly the following fungi: 

Merulius lachrymans, Figs. 15 and 16, and other members of the 
Merulius genus. 

Coniophora cerebella (or Coniophora puteana), Figs. 17 and 18. 




Figure 15. Merulius lachrymans, or dry rot, with fruit, 
on beam removed from cotton factory in canada. scale 
one-third natural size. 




Figure 16. Merulius lachrymans growing on a Southern 

PINE BEAM in THE BASEMENT OF A COTTON STOREHOUSE IN 

Rhode Island. Scale one-third natural size. 



19 




Figure 17. Coniophora, with fruit, on a beam removed 
from a cotton factory in canada. scale one-third 
natural size. 




Figure 18. Coniophora on a hemlock beam in a basement 
OF A Massachusetts cotton factory. Scale one-quarter 
natural size. 



20 

The dry rot disease is widely distributed in this country, 

but it has been more carefully investigated in Europe, especially 
.in Germany. Forty dry rot cases have been brought before the 
German courts within the last ten years. ^ 

In past years, little careful study has been given to the disease 
in this country, but the occasional cases recorded^ indicate that 
it was more a question of the general use of material of high 
natural resistance than the absence of the disease. The fact 
that the disease recently has shown itself on susceptible material 
in widely separated parts of the country, at about the same 
time, adds weight to this theory. Within the past three 
years, I have found well defined fruiting plants of the Merulius 
lachrymans in Quebec, Ontario, Massachusetts, Rhode Island, 
Louisiana and Mississippi. Coniophora has been found in 
Quebec and Massachusetts. 

Fruiting fungi can be easily identified, but it is difficult 
or impossible to positively identify the young sterile growth. 

The chief use in identification is to help in determining 
the best curative measures to apply. For example, the 
Lenzites can stand high temperatures, nearly up to the boiling 
point of water ,^ while the dry rot family are killed at a com- 
paratively low temperature, which peculiarity suggests a curative 
process to be explained later on. 



1. Hausschwammforschungen, Vol. 2, 190S, and Vol. 5, 1911. 

2. Charles T. Main, Notes on Mill Construction, page 31. 

3. Hausschwammforschungen, Vol. 3. 



21 



The name Polyporus family (fungi having many pores) has 
been used to include broadly any of the pore fungi having pores 
or holes of various sizes and shapes in the fruiting surface. 
Members of this family, which are conspicuous for the de- 
struction which they have caused, are Fames roseus (or Fomes 
carneus), Figures 21 and 22, Trametes serialis, Figure 20, and 
Lenzifes sepiaria. The last has pores shaped more like gills, 
see Figure 19, and is very active in destroying storehouse plat- 
forms. A few plants of this variety have been found on weave 
shed roof planks. It may be important as a destroyer of weave 
shed and paper mill roofs, but more investigation is needed to 
estabHsh that fact. 




Figure 19. Lexzites szpiaria ox spruce roof plaxk re- 
moved FROM A ^Massachusetts Cottox Factory. Scale 

FULL size. 




Figure 20. Trametes serialis from basemext of a ^Massa- 
CHUSETTS Cottox Factory. Scale full size. 



22 




Figure 21. Fames roseus (a hard rose tinted fungus) on beam 

FROM A PAPER MILL IN NORTHERN NeW YORK. SCALE ONE- 
HALF NATURAL SIZE. 




Figure 22. Fames roseus on a hemlock beam in a moist base- 
ment OF A Massachusetts cotton factory. Scale one- 
tenth natural size. 

In many cases, owing to the absence of fruiting plants, 
the particular kind of fungus causing the destruction can- 
not be determined. It is generally impossible to tell with 
any degree of certainty, from the appearance of the rotted 
wood, what fungus is responsible for the destruction. 

There is undoubtedly difference in the microscopic appear- 
ance of the fungus plants in the wood cells, as can be seen from 
some of my photo-micrographs, reproduced in Figures 23, 24 
and 25, but their peculiarities have not been much studied or 
described in the treatises available.^ 

1. Zersetzungserscheinungen des Holzes, Robert Hartig, 1878. 



23 




Figure 23. Coniophora in loblolly pine wood cells, 
magnified about 400 diameters. section tangent 
to the tree. 




Figure 24. Fungus passing through loblolly pine wood 

CELLS, PROBABLY TrAMETES SERIALIS. MAGNIFIED ABOUT 
400 DIAMETERS. SECTION TANGENT TO THE TREE. 




Figure 25. Ceratostomella pilifera, or blue sap pine 
fungus, in wood cells. magnified about 400 diameters. 
Section tangent to the tree. 



24 



THE RAPID PROGRESS OF DRY ROT. 

In most cases, the rotting found has taken place rapidly, 
instead of having been, as sometimes supposed, a slow 
continuous process similar to the rusting of iron or weathering 
of stone, and to be looked for chiefly in old buildings. Some- 
times, after the timber has been partly destroyed, the fungus 
growth is arrested, leaving sufficient strength to carry the load, 
and, when the rotted timber is discovered years later, it is as- 
sumed that the destruction has been progressing slowly since 
the erection of the building. 

In a case recently examined, the timbers in an old building 
were found considerably rotted at the bearing ends. Investi- 
gation indicated that the rotting occurred and stopped at least 
twenty -five years ago. In another case, the beams in a weaving 
mill basement were found seriously rotted at the end of ten 
years. They were replaced with similar beams of the same 
material, with the expectation that they would last another ten 
years at least. Many of these rotted in two years. The living 
fungus growing on the floor against which they were placed 
rapidly invaded the new material, which was green and there- 
fore contained sufficient water to make it subject to immediate 
attack. 

The entire frame of a factory in Canada was replaced after 
three years' service. Nineteen floor beams were removed from 
a Connecticut mill after two years' service, one beam actually 
breaking under a light load. The planking of several weaving 
mill and paper mill roofs has rotted so badly that they were 
replaced in from nine to fourteen years. 



25 

EFFECT OF HUMIDITY ON THE PROGRESS OF ROT. 

Dry rot progresses much faster in summer than in winter in 
an ordinary building which is heated and thus has its air made 
relatively dry during the winter months. Moist air gives 
the condition most favorable for rapid rotting. 

The average relative humidity of a building heated to 60° 

F. in winter, without artificial moisture, under conditions of the 
external atmosphere which have prevailed in Boston for the 
past ten years, is shown by the following curve. The curve for 
the summer months is the humidity of the outside air taken 
from the government records. 



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JAN. 



FEB. MAR APR. MAY JUNE JULY AUG. 5EPT OCT NOV DEC 



Figure 26. Giving the average relative humidity at Boston 

FOR the past ten YEARS, BOTH OUT OF DOORS AND INSIDE A 

building heated to 60° F. in winter. 



If the building is colder than the outside air in summer, or 
heated to less than 60° F. in winter, the relative humidity will 
be proportionately higher. 

If there is a source of moisture in the building, such as a moist 
basement, a leaky steam or water pipe, water from drying cloth, 
paper, or moist cotton, or from artificial humidifiers, the air will 
be further moistened. These sources of moisture generally act 
locaU}'-, causing a higher relative humidity in one part of the 
room than another. Near a cold pipe, or a cold roof or wall, 
the relative humidity may be increased without change in 
the absolute humidity, that is, the number of grains of 
moisture in a cubic foot of air. The relative, as well as the 
absolute humidity, may be locally increased; for example, by a 
leak in a steam pipe, the presence of a humidifying head, or 
vapor pot, or a bale of moist cotton. In studying the effect of 
moisture on dry rot, one must carefully distinguish between 
relative humidity and absolute humidity. 



26 

Relative humidity is simply the ratio of complete saturation, 
or the per cent of saturation, of the air at the given temperature, 
while absolute humidity is the actual quantity of water in the 
air, regardless of temperature. The relative humidity corre- 
sponding to a given constant quantity of water in a cubic foot 
of air changes greatly with the temperature, in other words, 
warm air will contain a much larger quantity of water than cold 
air. 

The amount of water required for saturation, that is, for a 
relative humidity of 100% at a barometric pressure of 30 inches, 
varies with the temperature, as follows: 

100% Relative Humidity at Grains Water per cu. ft. 



90° F. 


approximately 


15 


80° " 


" 


11 


70° " 


a 


8 


60° " 


a 


6 


50° " 


" 


4 


40° " 


a 


3 



One gallon of water would produce saturation when distributed 
through 7740 cubic feet of air, at a temperature of 65° F., equiva- 
lent to a room 10 ft, high x 20 ft, wide x 39 ft. long; and a 
quart of water, in the same volume of air, would give a relative 
humidity of 25%. 

The relative humidity at any temperature is the per= 
centage which the humidity found bears to that required 
for saturation. For example, if air at 70° F, was found to 
contain four grains per cubic foot, the relative humidity would be 
50%, since eight grains are required for saturation at this tem- 
perature. Looked at in another way, if external air in Decem- 
ber, having an absolute humidity of two grains of water per cubic 
foot at a temperature of 30° F,, is taken into a room heated to 
60°, its relative humidity becomes decreased from 100% to 30%. 
although its absolute humidity remains almost unchanged. 

The most convenient and accurate method of measuring 
relative humidity is by means of a sling hygrometer, which con- 
sists of two thermometers held in a suitable frame, so arranged 
that it can be whirled about rapidly through the air. One 
thermometer has the bulb enclosed in cloth which is moistened 
with water. The evaporation of water from this bulb causes a 
decrease in the temperature which is proportional to the rela- 



27 

tive humidity. This quantity can therefore be found by use 
of tables which accompany the instrument. 

Another instrument in common use in cotton mills makes use 
of the same principle, but the thermometers are fastened to a 
fixed standard and moisture is continuously supplied to the 
cloth about the wet bulb by means of a wick from a small bottle 
of water. This instrument will indicate too high humid- 
ity unless the air is circulated about the wet bulb by 
fanning or otherwise. In a measurement recently made with 
this form of instrument, it indicated 70% as it stood; after 
vigorous fanning, it indicated 55%. 

Neither form of instrument is suited for use in very small 
spaces, such as the opening about the bearing end of a beam, 
as the moisture evaporated will in itself change the rela- 
tive humidity and the circulation necessary for accurate meas- 
urement will introduce further disturbance. The instrument 
best suited for confined situations makes use of the ex- 
tension and contraction of a hair with the relative humidity. 
A fair degree of accuracy can apparently be obtained with this 
instrument if it is calibrated from time to time. 

A case recently investigated in a cordage factory, where several 
strips about 4 ft. wide rotted in the three inch plank flooring the 
entire length of the factory under spinning machines, which were 
evaporating considerable quantities of water, shows the effect of 
locally increased atmospheric humidity. The same form of 
floor when not in the immediate vicinity of this humidifying 
process has remained perfectly sound. The average relative 
humidity in the room is from 50% to 60%, while that directly 
under the machines is the greater part of the time at nearly 100%. 



28 



DRY ROT AND DAMP ROT. 



Most rot in mill timbers is caused by one or the other 
of two groups of fungus, — one thrives in dampness, the 
other in air relatively much drier. 

Those belonging to the dry rot group, consisting of the Merulius 
lachrymans and Coniophora, have been found in upper floors of 
reasonably dry mills and are able to thrive with a scant water 
supply. The dry rot fungi have been particularly destructive 
to new buildings, and have generally attacked the larger beams 
of the frame. 

The other group — which we may designate as damp rot fungi 
— consisting of members of the Polyporus family, requires a 
much larger water supply, and is particularly destructive in 
poorly ventilated basements. I have found two varieties in 
several basements, which Mr. C. J. Humphrey, Pathologist in 
the United States Forest Service, has kindly identified for me. 

The Fomes roseus, shown in Figures 21 and 22, is pink and 
covered with small round pores. The pink color is not con- 
fined to the surface, but goes through the plant and frequently 
extends a little way into the wood. Another variety found 
with great frequency in moist basements is the Trametes 
serialis, which has a tough, white fruiting surface covered with 
small pores. See Figure 20. 

Undoubtedly the growth of both of these pore fungi can 
be arrested by moderate drying. They seem to grow most 
luxuriantly when the relative humidity is nearly or quite 100%. 
In a basement recently examined, which was 175 ft. wide with 
windows on one side only, the relative humidity varied from 
about 50% near the windows to 100% on the further side, 
where there was no circulation of air. In the area which was 
most of the time at about 100%, there was an abundance of 
fruiting plants of the Trametes serialis and Fomes roseus. The 
floor had only been in five years. The spruce planks were 
completely destroyed, and the yellow pine beams somewhat 
attacked by the fungus. See Figure 27. 

Openings were made in the outside walls and a slight circula- 
tion of air obtained, so that the ordinary atmospheric humidity 
was reduced to about 80%, to 90 %o. with the result that the 
growth of the fungus was arrested. 



29 




Figure 27. 12" x 16" yellow pine beam and 4" spruce floor 

PLANK destroyed IN FIVE YEARS BY FUNGUS IN A MOIST BASE- 
MENT IN A WOOLEN MILL IN MASSACHUSETTS. SCALE ABOUT 
ONE-SIXTEENTH NATURAL SIZE. 



In another basement where these two varieties were growing 
luxuriantly, the Fames roseus was found only in the parts which 
were at practically 100% humidity most of the time. The 
Trametes serialis was found in the drier parts with an atmos- 
pheric humidity in the neighborhood of 90% to 95%. 



LOCAL DIFFERENCES IN EXPOSURE TO MOISTURE. 

The relative humidity of air in a room, or basement, 
sometimes is very different in places only a few feet apart, 

and, in studying cases of infection, careful note must be taken 
of these differences. 

An ordinary method of measuring the atmospheric humidity 
by means of a sHng hygrometer gives the average humidity 
over a considerable space. An example is shown in Figure 28, 
of locally increased relative humidity. 




Figure 28. Floor beams rotted off by increased rel- 
ative ATMOSPHERIC HUMIDITY CAUSED BY A COLD WATER 
PIPE.l 

In this case, a cold water pipe passes under several beams in 
a basement, the average humidity of which is in the neighbor- 
hood of 90%. The lower temperature in the vicinity of this 
pipe causes an increased saturation up to 100% at the pipe. 
The beams directly over it are rotted for a distance of eighteen 
inches to two feet away from the pipe, as can be seen in the 
photograph. 

1. The distinction between Relative Humidity and Absolute Humidity 
should be clearly understood. "When the term humid or humidity is used 
in every day talk, relative humidity is meant, not absolute. Relative 
humidity is the percentage of complete saturation that the air happens to 
contain at the given time and changes with the temperature, while the 
absolute quantity of water per cubic foot of air remains unchanged. The 
presence of the cold water pipe shown above increases the relative humid- 
ity of the air near it simply by lowering its temperature, while the num- 
ber of grains of water in each cubic foot of this air remains almost un- 
changed. 



31 



Dry and wet are only relative terms. The degree of dryness 
is of the greatest importance. The sHght difference of a few 
percent in the relative humidity is sufficient to stop the growth 
of certain fungi. The growth of the fungus depends more upon 
the relative humidity than upon the number of grains of water 
per cubic foot. It is also doubtless considerably influenced by 
the temperature. The effect of saturation of moisture is not 
limited to the air, but extends to the interior of the timber, as 
is shown by the rotted tank stave shown in Figure 30. 

Weaving room and paper mill roofs are frequently found 
with a sound shell both inside and out, and the interior entirely 
rotted away. Sometimes the zone of greatest rotting is nearer 
the outer roof covering, and sometimes nearer the inside of the 
building, according to the relative atmospheric humidity. 




Figure 29. Edges of two spruce planks from a weaving 

MILL roof showing ROT INSIDE. SCALE ONE-QUARTER 
NATURAL SIZE. 



Certain processes of manufacture require the atmos= 
pheric humidity to be regulated within narrow limits. ^ 

If it so happens that this humidity is sufficient to keep the 
timber or planking near the condition reqmred for the most rapid 
gro\\i;h of a common timber destroying fungus, as is frequently 
the case in weaving and paper mills, exceptional care must be 
given to selecting a resistant variety of timber, and to giving 
it a suitable antiseptic treatment in order to prevent serious 



1. Cotton carding rooms are frequently maintained at a relative humidity 
of 50% to 60% , and weave rooms from eO% to 80^. Paper mills are much of 
the time at nearly 100% in the vicinity oi" the paper machines or at the ceil- 
ing. In many textile processes, the humidity is maintained at a high percentage 
continuously day and night the year round, the tendency being constantly 
towards higher humidities and more careful distribution and regulation. 



32 

rotting. If, however, conditions of manufacture do not demand 
high humidity, and it can be kept down to 50% during most, of 
the time, there is little danger of serious rotting of good timber, 
if it is dry when installed. 

It is probable that a very important factor in the re= 
sistance of several woods to fungus is the presence of 
some moisture resisting material such as resin, which pre- 
vents sufficient water from being absorbed at the ordinary 
range of atmospheric saturation for the requirements of common 
fungi. On the other hand, the presence of hygroscopic materials 
in wood which cause it to absorb larger amounts of water, in 
order to come into equilibrium with a given atmospheric satura- 
tion, would render it more susceptible to attack by fungi. 



33 

EXTREMES OF WETNESS AND DRYNESS BOTH 
PREVENT ROT. 

Figure 30 shows a plank from the bottom of a tank, in which 
the fungus grew through a narrow space in the middle, the inside 
next the water being too wet for it and the outside next the 
air, too dry. 

That wood destroying fungi cannot grow under water, or with 
the wood cells filled with water, is proved by many examples. 

One of the fine points in the successful design of wood stave 
pipe from two feet to ten feet in diameter, for conveying water 
under pressure, is to design its staves so thin that the pressure 
will keep the wood saturated; then it will last almost indefi- 
nitely without decay. 

Penstocks have sometimes been covered with clay to prevent 
evaporation and keep the cells full of water. 




Figure 30. 2Y' Plank from a water tank. 

Wood of great antiquity has been found buried in clay, 
in a perfect state of preservation. ^ Piles under an old 
London bridge were found sound after being in the water 600 
years.2 The roof beams of the Basilica at Rome were found 
sound after a thousand years' use under conditions of dryness.^ 
In deep test borings for engineering structures, samples of buried 
logs are brought up in a good state of preservation after burial 
in wet earth since the glacial epoch. 

In popular phrase, "rot comes between wind and water." 

1. North American Gymnosperms. Penhallow. 

2. Destruction of Wood by Fungi, Buller, Science Progress, Vol. Ill, No. 2. 

3. A Treatise on the Resistance of Materials, D. V. Wood, 1883. 



34 

The weaving rooms of cotton mills are frequently main= 
tained at a saturation of moisture of 70% to 80% during 
working hours. With 70% saturation and a temperature of 
80° F., a decrease in temperature of 12° at night would cause 
precipitation, or increase the saturation to 100%. Rot in roof 
planks and the bearing ends of beams is doubtless chiefly due 
to this condition. The roof and walls of a manufacturing build- 
ing are colder than the air in the room for a considerable part of 
the year, therefore the air in contact with these cooler parts of 
the structure will be at a higher relative humidity than the 
average of the room. In the summer months, when these con- 
ditions do not hold, the outside humidity is high much of the 
time, so that the roof planks and beam ends in a highly humidified 
mill get little chance to thoroughly dry out at any part of the year, 
and antiseptic treatment of the timber is the only certain re- 
liance against decay. 

The Limits of Dampness Required for Growth of Dry Rot 
Fungus. 

Dry rot, or Merulius lachrymans fungus, will grow on the 
surface of wood at atmospheric saturations from 96% to 100%.^ 
It will grow inside of large beams of susceptible material at a much 
lower atmospheric saturation. In one case investigated, the 
room was maintained at less than 70% relative humidity, yet 
a large proportion of the beams supporting the second floor were 
destroyed within two years after the factory was completed. 

A possible source of moisture for supplying the require= 
ments of a fungus growing inside a large beam is the 
decomposition of the wood itself. Chemical analysis shows 
rotted wood to contain less hydrogen and more carbon than the 
original sound wood,^ therefore the hydrogen part of the cellulose, 
or lignine molecule, is more strongly attacked than the carbon 
part. This would result in the formation of water if the decom- 
position is accompanied by complete oxidation. Wood under- 
going bacterial decomposition under water forms marsh gas in 
large quantities. This may be formed to some extent when 
wood rots in the air, but apparently considerable water is also 
formed as shown by some direct measurements by Dr. Mez.^ 
This explains why fungus may thrive for some time in an at- 

1. Hausschwammforschungen, Vol. 6, page 308, MocUer, Jena, 1912. 

2. Cellulose, Cross and Bevaii, 1903, page 239. 

3. Der Hausschwamm, Dr. Carl Mez, Dresden, 1908, page 192. 



35 

mosphere of lower relative humidity, if established deeply in 
beams of large size, from the interior of which the water 
formed by the decomposition of the wood is but slowly 
evaporated. 

In a recent case, fungus appeared on the floor beams under a 
weave shed, about 300 feet wide, within a year after the building 
was completed. The beams were about four feet above a damp 
swampy soil. The builders, appreciating that the conditions 
were unfavorable, gave the beams a brush treatment with a coal 
tar preservative, and provided large open windows, at frequent 
intervals, for ventilation. The beams evidently contained living 
fungus when received. The ventilation prevented growth of 
the fungus on the surface of the wood for fifty or sixty feet from 
the windows. Beyond this, an abundant growth appeared. Meas- 
urements showed the relative humidity to be nearly 100% in 
the middle of the building, and 60% at forty feet from the 
windows. 
Ventilation Not Always a Cure. 

Ventilation is generally the first preventative measure sug- 
gested. Dry wood, which is placed in an atmosphere well below 
the moisture requirements of a given fungus, is undoubtedly 
incapable of infection with that fungus ; but, ventilation does not 
necessarily cause drying, as the wood will come into equilibrium 
with the moisture in the air and will become drier or wetter in 
proportion to the relative humidity of the air with which it is 
ventilated. Therefore timber ventilated with moist air may 
have its rate of rotting accelerated rather than retarded. As 
an example, a thoroughly waterproof covering for a column, 
which had been completely dried, would be more useful than 
a hole through the center for ventilation, if this column was 
used in a moist paper mill. 
Paint Sometimes Retards, Sometimes Accelerates Rotting. 

A heavy coat of paint may accelerate or retard the rate of 
rotting, depending upon whether it prevents the wood from 
absorbing or giving up moisture. The condition most com- 
monly met, in which paint causes rotting, is when it is applied 
to green timbers saturated with water. With dry sound timbers, 
which are to be placed in a moist atmosphere, a paint will 
doubtless prove beneficial in proportion to its waterproofing 
power. "Cold water" or "fireproofing" paints, containing hygro- 
scopic materials, would be expected to accelerate the progress 



36 

of rot, because they would attract moisture from the air and 
increase the moisture in the wood, as in the case of a building 
in Italy, in which chloride of lime was used as an antiseptic, with 
the result that the chloride of calcium attracted moisture and 
caused the rapid destruction of the building by fungus. 

The conditions required for germination and growth of 
the Mertilius lachrymans often have been mysterious. 

The spores germinate in an eccentric manner and frequently 
refuse to grow to fruition on their customary host in artificial 
cultures. Hartig stated that an alkaline medium is necessary, 
but it has since been shown by several investigators that an acid 
medium is required for the growth of the plant. The degree of 
acidity and the kind of acid is important. Falck shows that 
acetic, formic or carbonic acids are poisonous to it, while malic, 
citric and tartaric, in dilute solution, favor its growth. 

Long Life of Dormant Fungi. 

Dry rot fungi have two methods of reproduction and 
can remain a long time in a resting state. The common 
reproductive body, corresponding to the seed of higher plants, 
is called a spore, and grows over the surface of the plant. They 
are of brown color and therefore may be easily distinguished 
from the surrounding sterile growth, as can be readily seen from 
Figures 15 and 16. The spores are microscopic in size, being 
about .0004 of an inch long and .0002 of an inch broad. A single 
plant produces many millions and their small size allows them 
to float long distances in the air. 

Under unfavorable conditions for growth, such as insufficient 
moisture, some of these destructive fungi assume a form of 
reproduction different from that by which they ordinarily spread. 
In this form, the growing plant separates into small sections which 
can sprout and grow again when favorable conditions arise. 
It can remain in this resting state for a considerable time in air 
dry wood. Some of this dormant fungus is shown in the photo- 
micrograph, Figure 23. 

I have some specimens from a beam which was removed from 
a mill two years ago. Cultures from time to time show the 
Merulius lachrymans, which it contains, to be still living. 
Mez^ mentions a case in which this variety of fungus remained 
alive for four years and eight months, in a dry museum cabinet. 

1. Der^Hausschwamm, Dr. Carl Mez. 1908, page 63. 



37 



HOW THE DRY ROT DISEASE IS SPREAD. 



This disease is chiefly spread by direct contact, but living 
spores carried in the air can take root when they find a 
favorable resting place. 

Fungi are frequently carried in lumber^ and spread by plac- 
ing it in large piles with scant ventilation. As a result of this, 
beams are often found more deeply infected in the middle than 
at the ends. 

The separation of lumber in the piles by the use of sticks con- 
taining living fungus is another fruitful source of infection. 
Susceptible timber placed on rotten supports near the earth 
quickly becomes diseased. This is now avoided in several 
lumber yards by the use of concrete supports as shown in 
Figure 31. 




Figure 31. Concrete supports for lumber piles. 



I. Bulletin No. 13, U. S. Division of Forestry, page US. 



38 

HEAT AND DRYING ARE USEFUL IN STOPPING ROT. 

Often an infected building can be sterilized by skilful 
use of its own heating system. Merulius lachrymans is 
particularly sensitive to heat, a temperature of 108° F. for 
three hours, or 115° for one hour, being sufficient to kill it.^ 
It is also killed by complete dryness.^ But ordinary air drying 
does not destroy it. 

The particular varieties of fungi that destroy roof planks 
are undoubtedly more sensitive to dryness and less sensi- 
tive to heat than dry rot. It is therefore probable that 
heating a v/eave shed or paper miU roof will have little bene- 
ficial effect unless it is infected with lachrymans or Coniophora. 

Heat as a means of destroying lachrymans and Conio= 
phora in mill beams was tried recently, at the suggestion 
of the writer, on a large mill, in Canada, which was badly infected 
throughout; but, later, it was found that the disease had already 
progressed so far before the heating was applied that the struct- 
ure had become unsafe, therefore the beams had to be replaced. 
This removal of a thousand beams and columns gave an excel- 
lent opportunity to test the efficiency of the previous heat 
treatment by cultivating samples from those beams in which 
the infection was the deepest. . This treatment had comprised 
heating the mill four times, to about 115° F., by use of the steam 
heating system in warm weather, from Saturday noon until 
Monday morning, the temperature being carefully regulated 
by use of thermometers placed at the ceiling. 

In applying this heat treatment in mills protected against 
fire by automatic sprinklers, care must be used not to open or 
permanently injure the sprinkler heads. The temperature of the 
air should be kept 50° below the melting point of their fusible 
solder, which ordinarily is about 165°. 

Specimens were cultivated from forty of the badly rotted 
beams and only four showed living fungus. One hundred and 
three beams removed and left on the ground for several months 



1. Hausschwammforschungen, Vol. 1, 

2. Hausschwammforschungen, Vol. 6. 



39 



were examined superficially, and, in all of these, only six showed 
suspicious threadlike growths. The window frames and hollow 
roof were not sterilized by this treatment. Some of the few 
living cultures found came from the ends of beams which were 
imbedded in the brickwork where the heat could not readily 
penetrate, and some of the beams left on the ground may have 
become reinfected. 

On the other hand, beams removed from the mill before it 
was heat-treated showed a vigorous growth of fungus on cul- 
tivation, and also the formation of normal fruiting plants when 
left lying in the yard. 

While the results of this one practical experiment are not 
absolutely conclusive, they are very encouraging and indicate 
that the small cost of putting steam on the heating coils 
is well worth trying, if there is any suspicion of dry rot in 
a new building. 




Figure .32. Threadlike sterile fungus plant on end of a 

ROTTED MILL BEAM. SCALE ONE-QUARTER NATURAL SIZE. 



40 

Heating will probably prove more efficient in the few scattered 
superficial infections of a mill just completed than it did in this 
mill where the growth had been in active progress for two years 
or more and had deeply penetrated the susceptible material. 

The special heating will also increase the rapidity of drying 
and thereby tend to limit the spread of the disease through the 
agency of the rapidly growing threadlike plants. These growths 
pass rapidly along the splines of moist floor planks and through 
holes in moist columns, or openings between double beams, and 
can thereby quickly reach most of the susceptible material in 
the building. The most serious cases of rapid spread of the 
dry rot fungus that I have yet investigated have occurred where 
sappy or non-resistant material, exposed to the weather, re- 
mained in a water-soaked condition until it was covered, so that 
it could not dry out. The drying will also arrest other vari- 
eties of fungi than the lachrymans. 



41 



HOLES IN COLUMNS AND DOUBLE BEAMS WILL NOT 
PREVENT ROT. 

One of the reasons given for bored columns and 
double beams has been to prevent dry rot, and considerable 
importance has sometimes been given to this feature.^ 

Undoubtedly columns with holes through them, and thinner 
beams, would dry out quicker if given a chance to season, but 
the common custom of boring green or wet columns just before 
they are put in place in the building, and using moist lumber 
for double beams, leaves ideal places for the growth of fungus, as the 
air in the openings may be nearly saturated with moisture. The 
holes in the columns have the additional objection of forming a 
convenient passageway for the fungus to pass rapidly from 
floor to floor before the building has dried out. 

Untreated Carolina pine used for interflooring sometimes 
serves not only to infect the mill, but to carry the infection to 
all susceptible beams or planking in the floor. 




Figure '.i'.i. Central cross sectiox of lU " x 10" Southern 

PIXE COLUMN BORED FROM OPPOSITE ENDS. HOLES DO NOT 
COME TOGETHER IN CENTER AND FUNGUS CAN BE SEEN IN EACH 
HOLE. 

1. Engineering News, Vol. 62, 1909, page 620. 



42 




Figure 34. 10" x 10" column, shown in cross section in 
Figure 33, split through the holes, showing the fungus 
inside them more clearly. The holes are one and 
one-half inches in diameter. 




Figure 35. Cross section in center of a 10" x 10" loblolly 

PINE column, badly ROTTED, IN A COTTON FACTORY AFTER 

three years' service. Note that the hole through this 

column did not prevent it from ROTTING, 



43 










1 






1 • 






\ 




^ 


1 . 


^ 




# 1 - 


iaL 



-*s 



Figure 36. Front beam of a pair of double 8" x 18" beams 

HAS BEEN removed SHOWING DRY ROT FUNGUS GROWING IN 
THE SPACE BETWEEN THE BEAMS. 




Figure 37. Dry rot fungus growing along hole bored 

IN OAK COLUMN. SCALE ABOUT ONE-THIRD NATURAL SIZE 



44 



SLOW BURNING CONSTRUCTION. 



The following drawings show two examples of slow burning 
factory construction which are in common use. One, a several 
story building of moderate width; the other, a one story building 
which may have any width, as it is lighted by means of windows 
in the sawtooth roof. The basement of the latter form of con- 
struction gives trouble from rotting timber if the building is 
located on moist ground, owing to the fact that it is practicably 
impossible to get a natural circulation of air through this base- 
ment in the widths of 200' or more, commonly used in weaving 
mills. 




Figure 38. Standard form of slow burning mill construc- 
tion, WITH BEAMS SPACED FROM 8 FT. TO 12 FT. ON CENTERS, 
AND HEAVY PLANK FLOORS. 



45 




Figure 39. Standard slow burning factory building with 

SAWTOOTH roof SUCH AS IS FREQUENTLY USED FOR WEAVING 
MILLS. 



Laminated Floor. 

In slow-burning timber construction, it has been customary 
in many cases where an unusually stiff floor is required, to use 
2" X 4" or ?>" X ^" planks, spiked together on edge, for forming the 
floors. This so=called laminated construction is very 
treacherous so far as rotting is concerned, particularly if 
the planks are not thoroughly dry when the building is 
covered in. In buildings several stories high, it is customary 
to lay the plank of the lower floors before the walls of the 
upper stories are complete, thus leaving them exposed to the 
weather until the roof is put on. Sometimes the floors become 
thoroughly water-soaked by means of the numerous cracks 
between the planks. The evaporation of this water is retarded 
by the great thickness of the floor thus formed of plank on 
edge and by the top flooring. This moisture encourages 
rotting. In storehouses, for which this form of floor is fre- 
quently used, the conditions are worse than in the manu- 
facturing rooms, because the storehouses are seldom artificially 
warmed in winter, thereby giving less opportunity for drying. 



'46 



Several such cases have been reported within the last few months. 
The following figure shows two pieces, 3" x 6" x 24", cut from 
some Southern pine planks from such a floor in a Chicago store- 
house, after six years of service. These floors were water-soaked 
by rains before the roof was put on, and, as the building was 
not heated, the process of drying out was very slow, with the re- 
sult that the floors throughout the entire building were con- 
siderably rotted. 




Figure 40. Pieces cut from S" x 6" Southern pine planks 
removed from the laminated floor of a chicago store- 
HOUSE AFTER SIX years' SERVICE. 



47 
VARIETIES OF TIMBER AVAILABLE. 

The different varieties of timber available for mill con= 
struction are fewer in number than those available for 
railroad ties, or for structural purposes requiring smaller or 
shorter pieces. At present, the material in almost universal 
use for columns and beams in factories of "slow-burning" type, 
in the United States, east of the Rocky Mountains, is Southern 
pine. 

Occasionally hemlock or spruce is used for columns of the 
smaller sizes. In the older mills, columns of white pine and 
oak are often to be found. 

Spruce and hemlock are frequently used for floor and roof 
planking. Indeed, until recently, spruce plank was the favorite 
floor material for New England mills. 

Douglas fir is occasionally used for columns, beams and floor 
plank in the Middle West and will probably be more used in the 
future. The greatest manufacturing districts of the country 
are within convenient reach of the Southern pine forests 
and Southern pine is undoubtedly used in much larger quanti- 
ties than all other varieties, spruce plank being next, and hem- 
lock, third. Therefore, careful study of the Southern pines is 
of the greatest importance. 

Cheapness As An Index of Quality. 

It is a significant fact that much of the best longleaf 
pine timber produced in the South is being shipped to 
Europe. The European buyers consider quality first and are 
wilHng to pay a higher price for good timber. Too many of the 
American buyers of mill timber are chiefly guided by price. 
Several lumber manufacturers, producing excellent longleaf 
pine timber, stated that they hardly considered it worth while 
to quote on true longleaf timber to the American trade, as mixed 
varieties, offered at a lower price, were practically certain to be 
accepted. 

Longleaf pine of merchantable inspection, Interstate Rules of 
1905, in sizes suitable for mill timber, can be had at the present 
time, I am told, at about $33 per M, delivered in New Eng- 
land, "Prime" grade would cost about three dollars more. The 
best quality "German Prime" would cost from $40 to $50. 



48 . 

COMMON VARIETIES OF SOUTHERN PINE. 

There is much confusion in local names. Mohr gives 
six Latin and twenty-nine common names as having been used 
at different times, or different places, for the longleaf pine; and, 
the other varieties of pine have nearly as many. The Cuban and 
longleaf pines are sometimes confused as both have long leaves, 
while the shortleaf and North Carolina both have shorter 
leaves. 

The positive identification of longleaf pine lumber is 
difficult or impossible.^ There are slight microscopic differ- 
ences in the form of the medullary rays of the North Carolina 
pine, as given by Penhallow^ and Roth,^ but to use them for identi- 
fication would require considerable experience in the microscopic 
study of the pines. The macroscopic differences are more 
striking with characteristic specimens. The longleaf pine is 
heavy, resinous and fine grained, averaging for the dry wood from 
the butt of the tree, according to Sargent, 43.7 lbs. per cubic foot. 
See Figures 42 and 43. 

The Cuban pine is slightly heavier, averaging 47 lbs. per 
cubic foot, resinous and coarse grained, with a large proportion 
of dense summerwood, and a much larger proportion of sap- 
wood. 

The North Carolina pine, also known as loblolly pine and 
frequently sold as shortleaf pine, is lighter, averaging 34 lbs. 
per cubic foot, somewhat less resinous, coarse grained, with a 
large percentage of sapwood. See Figures 41 and 44. 



1. Mr. Arthur Koehler, Expert in Wnod Identification of the U. S. Forest 
Products Laboratory of Madison, Wis., slates, in a personal communication, 
that recent discoveries which he has made, and which will be published by the 
U. S Forest Service in the near future, make it possible to always distinguish 
longleaf pine from shortleaf and loblolly, by the gross character in large 
pieces, and microscopically in small specimens. 

2. North American Gymnosperms, D. P. Penhallow. 1907. 

3. Bulletin No. 13. U. S. Division o' Forestry, 1897. 



49 

The shortleaf pine is moderately light, averaging 38 lbs. per 
cubic foot, the least resinous of the four, and of medium grain. 
See Figures 43 and 45. 

The fallowing are the weights per cubic foot given b}'- Alohr^ 
for kiln dried material,— longleaf 36 lbs., Cuban 37 lbs., short- 
leaf 30 lbs., and North Carolina 31 lbs. The reason for Mohr's 
weights being less than those of Sargent is that he takes the 
average of the tree, the top of which is much lighter, while 
Sargent considers only the heartwood at the butt. Mohr's 
weights are probably much nearer to the average timber now on 
the market than Sargent's. 



1. Bulletin No. 13, U. S. Division of Forestry, 



50 




Figure 41. Loblolly or North Carolina pine. {Finns 
tacda.) 

Rosin at A 14.6%, B 1.6%, C 3.1%. 

Density at A 26.3, B 26.8, C 27.9 lbs. per cu. ft. 

A, Heartwood ; B and C, Sapwood. 

Note the characteristic broad sapwood and dark grain bands, 
less clearly marked than those of the longleaf. 





Figure 42. Loxgleaf pine log 29" in diameter, {Pinus 
paliistris.) 
Note dark colored, well marked heart wood and comparatively 
thin sapwood, also fine grain bands with dark colored summer- 
wood. The resinous quality of the wood is indicated by the 
dark color. 



52 




Figure 43. Shortleaf pine. (Pinus echinata.) 
Rosin at A 23.3%, B 5.2%, C 4.4%, D 1.8%, E 2.3%. 
Density at A 33.7, D 32.5, E 31.1 lbs. per cu. ft. 
A, B, C, D, Heartwood; E, Sap wood. 



This wood is generally somewhat lighter in color, and less 
resinous in appearance than the longleaf. The dark summer- 
wood in the grain bands is also not quite so clearly marked. 



53 




Figure 44. Loblolly or North Carolina pine {Piniis taeda.) 
Rosin at B 1.9%, Density 26.5 lbs. per cu. ft., Sap wood. 
Note the characteristic broad sap wood and dark grain bands, 
somewhat less clearly marked than those of the shortleaf. 



54 




Figure 45. Shortleaf pine (Piiuis ccii'niata.) 

Rosin at A 4.6%. B 1.6%, Density at A 30.6, B 29.1 lbs. 

per cu. ft. 
Note that the wood is generally somewhat lighter in color, 
and less resinous in appearance than the longleaf. The dark 
summerwood in the grain bands is also not quite so clearly marked. 



55 




Figure 46. Loxgleaf pine log 28" in diameter. {Pinus 

palustris.) 

Note the dark colored, well marked heartwood and the com- 
paratively thin sapwood, averaging about 2|" in thickness. 
This timber, while undoubtedly longleaf pine, is inferior to that 
shown in Figure 42, as it is lighter in weight, less resinous and 
more subject to decay, as shown b}^ the fact that within a year 
after it was cut, rotting had started in the outer portions of the 
heartwood, although both sections were kept under identical 
conditions. 



56 



AVAILABLE SOUTHERN PINE. 



In some recent printed discussions,^ it is intimated that if the 
requirements of the purchaser are clearly made known to the 
lumber manufacturer, and he is willing to pay the price, as good 
pine timber can be obtained now as in the past. As an illus- 
tration of the practical conditions, we may cite a recent case. 
The president of a paper mill, requiring plank for a new roof, 
wrote at our suggestion to a large yellow pine lumber manu- 
facturing company, known to be cutting good longleaf pine 
at some of its mills. He stated clearly that he required 
good resinous longleaf plank for a paper mill roof and 
accepted the price named without question. The follow- 
ing photographs, Figure 47, show twelve of the planks received. 

The following table shows the wide variation in two of the most 
important qualities that determine strength and resistance of 
decay. 




Figure 47. 



Pine plank for a paper mill roof, 
about one-sixth natural size. 



Density 
1. 42 lbs. per cu ft 



33 

28 
41 
38 
42 



Rosin 



Density 



Scale 



Rosin 



5.6% 


7. 26 lbs. per cu. ft. 


3.0% 


2.5% 


8. 35 " " " " 


1.2% 


1.8% 


9. 40 " " " " 


7.9% 


2.4% 


10. 47 " " " " 


2.8% 


6.2% 


11. 31 " " " " 


1.6% 


6.9% 


12. 31 " " " " 


2.3% 



1. Proceedings of the American Society for Testing Materials, 1914, 
Part 1, page 385." 



57 

These samples fairly represent the entire lot, and they vary 
in density from 26 to 47 pounds, per cubic foot, and the 

rosin content varies from 1.8% to 7.9%. The lumber manu- 
facturer states that this is a fair average of the longleaf pine, 
"all heart" grade, now being shipped under the present grading 
rules. 

It is generally agreed, I think, by lumber experts, that there 
are few purposes for which lumber of this wide range of density 
will be equally serviceable. It is probably all longleaf pine, but 
some of it is poor longleaf pine. 

This shows clearly the need of a system of grading, by 
which the heavy resinous material can be separated from 
that which is light and porous, and each appHed to its proper 
use, suitable antiseptic treatment being given to the lighter 
material if the use requires resistance to decay. 

With this separation, all of it is more valuable than the mixture 
now being sold. 

In a recent discussion,^ it was stated by Mr. Howard F. Weiss, 
Director of the United States Forest Products Laboratory, 
that there is no difference between the longleaf pine now growing 
in the South and that which grew in past years. This is doubt- 
less true. Later, in the same article, is the following, — ' 'A number 
of other woods are now apparently being mixed with the Southern 
pines and are sold with them apparently without distinction. In 
this laboratory we have received Norway pine on contracts in 
which we called for longleaf pine." 

Mr. Knight C. Richmond, ^ in a recent discussion before the 
National Association of Cotton Manufacturers, makes the 
following statement. "One or two cases have come to my mind 
which show the limit to which this has been carried. In one 
case a vessel sailing from Portland, Oregon, loaded with Oregon 
fir in large sized sticks, sailed around to Boston harbor and the 
Oregon fir was sold to a lumber dealer, who promptly sent it 
over to a firm of contracting engineers under the specification 
of longleaf Georgia pine, and got away with it. 

One other case, which seems almost incredible, was a shipload 
of spruce^ sent down to Boston and then shipped back to the 
mill to build flumes with in a paper mill where they wanted a 
particularly good lot of Georgia longleaf yellow pine." 

1. Engineering Record, Jan. 12, 1914. 

2. Transactions at the National Association of Cotton Manufacturers, 
Vol. 96, April, 1914, page 283. 

3. This word was printed "cypress" in the printed discussion. Mr. 
Richmond states that this is an error, that it should h& " spruce." 



58 

The present definition for longleaf pine of the American 
Society for Testing Materials opens the way to such practices by 
giving a double meaning to the name ^^ longleaf pine.'''' So far as 
the present definitions of the American Society for Testing 
Materials go, almost any kind of wood, shortleaf, Cuban or 
North Carolina, can be sold under them as "commercial 
longleaf pine." 

In the first edition of this pamphlet, I quoted some figures of 
prices which had recently been paid for Southern pine timber, 
and drew the conclusion that selected, uniformly resinous long- 
leaf pine would probably cost $115. per thousand. These 
figures were ridiculed by lumber experts, attention being called 
to the prices quoted in the open market for "commercial longleaf 
pine" timber. "Commercial longleaf pine" may, or may not, 
be true longleaf pine, and is not necessarily sufficiently resinous 
to resist decay, or sufficiently dense to give the desired strength. 

It has not been possible to check the above mentioned estimate, 
because it has not been possible to get quotations on, or to buy, 
such excellently uniform and carefully selected material as that 
described. Therefore this question of price must remain open 
until such material is found available in quantity, under ordinary 
commercial conditions. 

(1) This definition reads : — 

"Southern Yellow Pine." Under this heading two classes of timber are 
used, (a) Longleaf Pine, (b) Shortleaf Pine. 

It is understood that these two terms are descriptive of quality rather than of 
botanical species. Thus, shortleaf pine would cover such species as are now 
known as North Carolina pine, loblolly pine, and shortleaf pine. "Longleaf 
Pine" is descriptive of quality, and if Cuban, shortleaf or loblolly pine is grown 
under such conditions that it produces a large percentage of hard summerwood, 
so as to be equivalent to the wood produced by the true longleaf, it would be 
covered by the term "Longleaf Pine." 



59 

ROSIN AS A CAUSE OF RESISTANCE OF WOOD TO 
FUNGI. 

The causes of natural resistance to fungi in wood are obscure 
and have been investigated but little. Tannins in moderate 
concentration oppose the growth of MeruUus lachrymans as 
shown by Wehmer.^ He finds, however, that they offer less 
hindrance to the Coniophora. The Daedalea quercina, on the 
other hand, thrives on tannin-rich woods; but this last named 
fungus has not been found important as a destroyer of structural 
timber, other than posts exposed to the weather. Moreover, 
woods containing much tannin are now little used for mill 
construction. 

Heartwood is Generally Much More Resistant to Fungi 
than Sapwood. 

The process of heart formation in trees is little known. In 
the Southern pines it generally takes from twenty-five to fifty 
years and is frequently attended with increase in the rosin. 
The photographic activity mentioned on Page 71 is much more 
noticeable in the heart than the sapwood of many trees, includ- 
ing the hard pines. In some of the oaks and locust, the tannin 
increases sharply at the line where the heartwood commences. 
The presence of starches and sugars in the sapwood, which 
serve as foods for fungi, as well as the greater water content of 
this part of the tree, is probably the chief cause of its more rapid 
destruction, while the resistance to water of the heart rosin and 
the antiseptic action of tannin are undoubtedly important 
factors in the resistance of the heartwood. 

The preservative power of rosin is frequently mentioned 
as a matter of general observation, but careful study into 
the cause has not been made. Penhallow^ mentions it. Mayr"* 
has analyzed many of the pines for rosin and shows some inter- 
esting facts in regard to its distribution in different parts of the 
tree, but he is guarded in his conclusions, being rather inclined 
to attribute the durability of pine heartwood to material which 
he calls "dauer stoff," in German, of which the nearest English 
equivalent is "durable material," and which he associated with 
the dark color of heartwood. 

1. Wehmer, Mycologisches Centralblatt, Vol. 1, 1912, pages 138 and 166. 
Vol. 2, page 331. 

2. Penhallow, North Araerican Gymnosperms, page 162. 

3. Mayr, Harz der Nadelholzer, 1899, pages 43-49. 



60 

Mayr's analyses tend to throw some light on observations of 
Hartig on the relative resistance to lachrymans of the heart 
and sap wood of Pinus sylvestris (Scotch fir), and Picia excelsa 
(Norway spruce), both European woods. Hartig^ finds that the 
sapwood of the Pinus sylvestris is attacked by lachrymans more 
rapidly than the heartwood, while the reverse is true with the 
Picia excelsa, as shown by the following figures, giving the 
average loss in weight of specimens infected with lachrymans 
and allowed to rot in contact with ashes, sand, coal dust, chips, 
etc. 
Percentage Loss of Weight by Rotting in Relation to 

Rosin Content. 

Pinus Sylvestris. Picia Excelsa. 



Heart. 
Dry Winter cut wood, lost in 
weight, 7.2% 


Sap. 
16.6% 


Heart. 

12.8% 


Sap. 
9.8% 


Moist Winter cut wood, lost 
in weight, 5 . 6 


16.4 


29.9 


14.9 


Moist Summer cut wood, lost 
in weight, 6 . 8 


14.9 


24.0 


22.0 



Average percentage loss in 

weight, 6.5 16.0 22.2 15.5 

Average percentage of rosin 

from Mayr's analyses, 4.5 3.0 1 . 05 1 . 68 

Note that with only 1.05% of rosin the loss was 22.2% while 
with 4.5% of rosin the loss was 6.5%, these two being for heart- 
wood, while for sapwood the difference was not large. 

The inverse ratio of the loss of weight to the percentage 
of rosin is in as close agreement as could be expected for 
quantities varying between such broad limits as the percentage 
of rosin in these woods. 

An experiment was made by the writer in which longleaf 
pine heartwood, out of which the rosin had been dissolved with 
benzole, was infected with Merulius lachrymans, together with 
a specimen of the original unextracted wood. After one year's 
exposure of each, the wood from which the rosin had been 
extracted was reduced in weight four times as much as the 
original wood, indicating that the rosin exerted a decided 
preservative action. 

1. R. Hartig. Der Echte Hausschwamm, 1902, page 44. 



CI 



In some of the pines, there is an abrupt increase in the 
rosin content at the line between sap and heart, as there 
is of the tannins, similarly, in some of the oaks^ and locust. 
There is also an abrupt change in the light-sensitive property 
of heartwood, which is associated with its dark color in some 
cases, but not always. 

The following rosin analyses of longleaf pine are given by 
the United States Forest Service. - 



Rosin Analvses. 



23 ft. from Ground. 



33 ft. from Ground. 



No. of 
trees 

4 
3 
3 
4 
3 



Sap 

1.48% 

1.76 

1.74 

1.78 

1.49 



Average rosin) 
in heartwood ( 



Outer 
heart 

6.78% 

4.35 

3.48 

4.67% 



Inner 
heart 

4.97% 

4.06 

6.29 

4.95 

2.47 



Sap 



1.35 



1.34 



Outer 
heart 



3.63 
3.70% 



Inner 
heart 

2.97% 
4.29 



2.79 



The following pages show some representative tests made 
by the author, to determine the rosin content and density of 
longleaf pine from several different places. 



1. G. Kraus, Physiologie des Gerbstoff, pages 128-129. 

2. Bulletin No. 8. Division of Forestry, 1893, page 49. 



62 



LONQLEAF PINE FROM THE FOOT-HILLS OF 
ALABAMA. 




Figure 48. 12" x 16" Longleaf pine from top of tree. 
Rosin at A 14.2%, B 1.8%, C 3.2% 
Density at A 29.2, B 29.3, C 25.0 lbs. per cu. fL 




Figure 49. 12" x 16" Longleaf pine from butt of tree. 
Rosin at A 13.6%, B 13.8%, C 9.8%. 
Density at A 31.0, B 33.7, C 28.4 lbs. per cu. ft., the average 
percentage of rosin at the butt being about twice that at the 
top. 



63 



LONQLEAF PINE FROM THE FOOT-HILLS OF 
ALABAMA. 




Figure 50. 12" x 16" Longleaf pine from top of tree. 
Rosin at A 9.6%, B 1.5%, C 2.7%. 
Density at A 27.5, B 35.0, C 27.8 lbs. per cu. ft. 



B 




Figure 51. 12" x 16" Longleaf pine from butt of tree. 
Rosin at A 25.7%, B 10.7%, C 8.5%. 
Density at A 37.0, B 35.5, C 33.0 lbs. per cu. ft., the average 
rosin at the butt being about three times that at the top. 



64 




Figure 52. Longleaf pine from Central Mississippi, 
section cut from tree 42' from ground. 




Figure 53. Longleaf pine from Central Mississippi, 

SECTION from BUTT OF SAME TREE. 



65 




Figure 54. Longleaf pine from Coastal Plain of Louisiana. 
Rosin at A 1.2%, B 10.8%, C 5.0%. 

Density at A 36.3, B 39.3, C 32.0 lbs. per cu. ft. 




Figure 55. Longleaf pine from Coastal Plain of Louisiana. 

Rosin at A 6.0%, B 17.2%, C 2.8%. 

Density at A 29.4, B 34.1, C 25.7 lbs. per cu. ft. 



66 




Figure 56. Resinous longleaf pine from Texas. 



67 

The longleaf pine heartwood shows a wide variation in 
the rosin content, as can be seen from the several analyses 
given. It is evident that the top of the tree is generally less 
resinous than the butt, although this is not a universal rule. 
This would indicate that the only generalizations which can be 
made as to the durability of longleaf pine, as indexed by rosin, 
are that the average longleaf pine is more resinous than the 
average wood of the shortleaf and loblolly, and, in the longleaf 
heartwood, the resin is generally more uniformly distributed. 
The light non=resinous longleaf pine from the tops of trees, 
or from trees which have grown under unfavorable conditions, 
doubtless is no more resistant to decay than similar non= 
resinous shortleaf. 

The following statement is taken from a recent German 
work entitled "Hausschwammforschungen" (or House Fungus 
Investigation), Vol. 3, page 178. 

"All wood destroying fungi attack coarse grained Scotch fir 
sap wood more readily than resin rich dense material. The 
Scotch fir heartwood under natural conditions is attacked with 
great difficulty even by Merulius domesticus, particularly in 
small cultures. Resin rich knots are practically immune." 

The rosin doubtless owes its antiseptic power chiefly to 
waterproofing qualities, preventing the progress of fungi by 
causing the wood to come into equilibrium with the average 
moisture of the air without sufficient water for their growth. Be- 
sides being present in the sapwoods of most of the pines in smaller 
quantities than in the heartwood, it is associated in the green 
sapwood with hygroscopic substances which annul its water- 
proofing action to a certain extent. 

Under the present system of grading and selection of 
Southern pine timber, the chief guarantee of durability is 
the proportion of heartwood. This is undoubtedly a sufficient 
guarantee for dry locations, if the timber itself has been well 
dried before it is put into the structure. Southern pine timber 
in a moist atmosphere cannot be depended upon, how= 
ever, unless its durability is assured by a high percent- 
age of rosin, or is reinforced by antiseptic treatment or^ 
preferably, both. 

Natural resistant woods, owing their durability to substances 
uniformly distributed in the tree, would be expected to be 



68 

superior to chemically treated wood, if the antiseptic material 
is sufficiently active for the conditions under which the wood 
is to be used. 

The percentage of rosin in the sound centers of rotted 
beams taken from a mill was determined in order to get 
an idea of the amount at which the fungus would not grow 

under ordinary mill conditions. See Fig. 57. 

In the poorest of hard pine, there is generally a sound center to 
rotted beams and this center contains more rosin than the 
remainder of the section. Sometimes it is not bounded by the 
growth rings but is very irregular, the cause being that rosin has 
been irregularly deposited in the section, owing to knots or 
injuries to the tree. The limits of the sound center are not 
always the same as those of the heartwood. There is some- 
times a much greater deposit of rosin at the center of growth 
than in the older wood. In some of the shortleaf pines this 
peculiarity is conspicuous. See Figure 43. 

It is apparent that the limiting amount of rosin which is 
just sufficient to stop the fungus is in the neighborhood 
of three per cent. 

The limiting power of rosin is undoubtedly not absolute, but 
varies with the moisture, variety of fungus, and time of exposure. 
Therefore, it is safe to assume that a mill beam should have 
four or five per cent of rosin throughout, to successfully with- 
stand fungus by its own power of resistance under ordinary 
conditions of dampness. Dye houses and paper mills would 
probably require more. 

Both the rosin content and the density can be conveniently 
measured by boring one inch holes 2" deep into the end of the 
beam, collecting the chips, drying and weighing them, then 
extracting the rosin from them with benzole, and weighing it. 

The boring should be done with a bit, without a spur, which 
cuts a smooth hole with a flat bottom and can therefore be easily 
measured. A hole one inch in diameter and two inches deep 
will have a cubical contents of .00091 cu. ft. 

. The rosin extraction can be made most conveniently by means 
of carefully distilled benzole and a Soxhlet extraction apparatus. 
The drying can be accomplished in an oven maintained at a 
temperature of 212° F. by water, electricity or other form of 



heat and should be continued until the specimen no longer loses 
weight. A chemical balance which is sensitive to one milli- 
gram should be used in the weighing. The specimens should be 
kept, after being dried until they are weighed, in desiccators with 
suitable drying agents such as strong sulphuric acid or calcium 
chloride. 

Cuban or North Carolina pine with 10% of rosin is apparently 
as resistant to fungus as longleaf pine with the same percentage. 
Heart without rosin is not immune. 



-70 



Rotted 12" x 16" Pine Beams Removed After Two Years' 
Service. 






Figure 57. 


Per 


CENT ROSIN 


. 




Center 


Medium Outer 




Center 


Medium 


Outer 


A 


B C 




A 


B 


C 


5.36 


7.04 .68 




29.21 


12.17 


.88 


4.46 


1.99 .76 




6.26 


6.56 


.58 


8.36 


4.89 1.17 




3.45 


18.81 


.99 


7.72 


5.12 .83 




9.45 


2.31 


.82 



71 
DURABILITY AND PHOTOGRAPHIC ACTIVITY. 

I have tried, by experiment, to learn if the photographic activ- 
ity of different woods had any relation to their susceptibility to 
decay, but without success. Nevertheless, the facts found seem 
of sufficient interest to be mentioned. 

The resistance of wood to decay does not depend upon 
any one factor alone, but is the result of many heterogeneous 
components acting together. The following phenomena may 
have some significance in this connection. 

Most woods after being exposed to strong light will act 
in the dark upon a photographic plate placed in close con- 
tact with the specimen. There are several constituents of 
the wood which can cause this activity, including rosin, turpen- 
tine and the wood itself. The photographic activity is the re- 
sult of an automatic oxidation reaction, to which many carbon 
compounds are subject. The action of wood on a photographic 
plate has been shown to be caused by hydrogen peroxide, or 
other form of active oxygen, given off when automatic oxidation 
is taking place. ^ The active oxygen may have some fungicidal 
power, but it alone cannot be of much antiseptic value, as the 
turpentine of the sapwood possesses the same property very 
strongly. 

Russell gives the following order of photographic activity for 
some of the commoner woods: — 



Very Active 


Moderately Active 


Slightly Active 


Oak 


Cedar 


Ash 


Scotch Fir 


Cherry 


Elm 




Maple 


Horse-chestnut 




Birch 






Spruce 






Locust 





The woods which are photographically active are also 
generally resistant to fungus, but this is evidently not a 
universal law, as cedar and locust are grouped with maple and 
birch. The condition of the specimen, however, is an important 
factor. The photographic activity is much increased by light, 
and one at least of the photo-active substances in wood is soluble 
in water. 



1. William J. Russell, Royal Society Transactions, Vol. 197, page 281, 
1903. Royal Society Proceedings, Vol. 78, page 385, 1906. 



SAP WOOD 



SCREENED FROM SUNLIGHT 





^EART WOOD 



Figure 58. Showing the effect on a photographic plate of 
heartwood and sapwood of red birch which had been 
exposed to sunlight, part of it being screened by a cross- 
shaped piece of tinfoil with a square hole in the center. 



It will be noted that the activity of the heartwood is more 
strongly increased by the sunlight than that of the sapwood. 
This phenomenon is also strongly marked in Southern pine and 
many other woods. The wood, after being exposed to bright 
sunlight for about two hours, shielded by the tinfoil, the tinfoil 
was removed and the wood was placed in contact with a rapid 
photographic plate and left in total darkness for a week. At the 
end of that time, the plate was developed in the customary man- 
ner, the image obtained being that shown in the picture. The 
heartwood had made a strong impression on the plate, excepting 
where it had been shielded from sunlight by the tinfoil. Ex- 
posure of the specimen of wood, either to direct sunlight or to 
a moderately elevated temperature, just prior to contact with 
the sensitive plate, apparently produces a similarly increased 
photographic activity. 



73 



DENSITY AS AN INDEX OF STRENGTH. 



The proportion between spring and summerwood has 
been suggested as a criterion for grading timber. This is 
now being favorably considered by some of the larger lumber 
manufacturing associations, and is undoubtedly much in ad- 
vance of present methods, as timber containing much sum- 
merwood is generally dense and strong. The proportion is 
difficult to determine with precision, however, particularly in 
material with fine or uneven grain. It is to be expected that a 
beam of irregularly distributed density will vary in strength, 
with the Hghter wood located at the neutral axis, or at the part 
of maximum stress. 

Weight per cubic foot of dry wood is a more accurate 
index of strength than the proportion of summerwood in the 
annual growth rings, which has been recommended as the best 
index of quality, and it can be obtained with greater precision. 

Light=weight wood is simply wood without much wood 
in it, in other words, all wood would weigh about 100 lbs. 
per cubic foot if it were solid. The difference between 
this and the actual weight gives the proportion of air 
spaces that it contains, as shown by the following photo- 
micrographs, made by the author, of transverse sections of 
Southern pine. See Figures 59, 60, 61 and 62. 




Figure 59. 



Line between spjiing and summerwood. 
Magnified about 15 diameters. 



74 




Figure 60. Very light springwood. 
400 diameters. 



Magnified about 






Figure 61. Moderately light summerwood 
ABOUT 400 diameters. 



Magnified 




Figure 62. Very dense summerwood. Magnified about 
400 diameters. 



75 

Density has been shown by numerous tests of the United 
States Forest Service to be a reliable index of strength of 
timber. 

The proportionality between density and strength in the 
middle of its range (from 30 to 40 lbs. with the longleaf pine) is 
considerably obscured b}- other variables, such as season cracks, 
knots, cross grain, etc., as shown in tests given b^^ the United 
States Forest Service.^ The range of density of shortleaf and 
loblolly is somewhat lower; therefore, only the best of these 
varieties will have a density above 30 lbs. per cubic "foot, and 
most of the poorer longleaf pine will have a density below this 
amount. 

Photo-micrographs made by the author, of transverse sec- 
tions of Southern pine of various densities, illustrate that density 
or weight per cubic foot is simply a measure of the amount of 
real wood present as distinct from air-filled cells. 

Johnson^ gives the following rule: "Cross-breaking strength 
of all timbers, except the oaks, in pounds per square inch=300 
times dry weight in pounds per cubic foot." 

The tests given by the Forest Service indicate that not much 
more than one-half of ^his amount can be depended upon with 
structural sizes of longleaf pine of average quality, the figures 
given being: 

Longleaf timber, green, 35 lbs. per cubic ft. dry weight, has a 
modulus of rupture of 6140. 

Longleaf timber, air seasoned, 39 lbs. per cubic ft. dry weight, 
has a modulus of rupture of 5691. 

Among the specimens from which these averages are taken, 
there is apparently only one below 32 lbs. per cubic ft. 

The moisture contained in wood is an important factor in 
its strength, as shown by many tests made by the United States 
Forest Service,^ longleaf pine and spruce increasing about 
300% in strength as the moisture is reduced from 30% to 0. 



1. Bulletin 108, "Tests of Structural Timber." 

2. J. B. Johnson, Materials of Construction, 1912, page 680. 

3. Bulletin No. 70, Effect of Moisture on the Strength and Stiffness of Wood. 



76 

SPECIFICATIONS FOR STRUCTURAL TIMBER. 

Many of the specifications for Southern pine in common use 
are vague or meaningless owing to the fact that the terms used 
are not clearly defined or are not determinable. For example, — 

"Best quality" could honestly be taken to mean either the 
best in the local market, or the best in the world. 

"Longleaf pine" in the form of lumber is practically impossible 
to identify beyond a doubt. " Shortleaf Cuban " and " loblolly " 
are regularly sold as "commercial longleaf." It can only be 
distinguished with positive certainty in the growing tree. 

"Georgia" is sometimes added to a specification for pine, 
but lumber grown in that state is seldom insisted upon, nor is 
its place of growth important. Some of the best Southern pine 
lumber now obtainable comes from Florida, Alabama, Missis- 
sippi, Louisiana and Texas. 

Specification of the American Society for Testing 
Materials. 
The definition which has heretofore been adopted by 
the American Society for Testing Materials practically 
calls all good material "longleaf pine" and poor material 
"shortleaf pine." The exact words being as follows:^ 

"Southern Yellow Pine." Under this heading two 
classes of timber are used, (a) Longleaf Pine, (b) Short- 
leaf Pine. 

It is understood that these two terms are descriptive 
of quality, rather than of botanical species. Thus, 
shortleaf pine would cover such species as are now 
known as North Carolina pine, loblolly pine, and short- 
leaf pine. "Longleaf Pine" is descriptive of quality, 
and if Cuban, shortleaf or loblolly pine is grown under 
such conditions that it produces a large percentage of 
hard summerwood, so as to be equivalent to the wood 
produced by the true longleaf, it would be covered by 
the term "Longleaf Pine." 

This is unfortunate in giving a double meaning to the names 
longleaf and shortleaf, which already have a generally accepted 
botanical meaning, and it is incomplete in not clearly defining 
the characteristics of the two classes. 

1. American Society for Testing Materials, Year Book ISlo, payes 302 and 
304. 



77 

The following are a part of the specifications for ^^ellow pine 
bridge and trestle timbers. No specific specifications for other 
structural timbers have as ^^et been made by this organization. 

"Except as noted, all timber shall be sound, sawed to 
standard size, square-edged and straight; shall be close- 
grained and free from defects, such as injurious ring 
shakes and cross grain, unsound or loose knots, knots 
in groups, deca^^ or other defects that will materially 
impair its strength. 

Standard Size of Sawed Timber. Rough timbers 
sawed to standard size shall mean that they shall not 
be over I inch scant from the actual size specified. For 
instance a 12 by 12 inch timber shall measure not less 
than 1 If by 11 f inches. 

Standard Dressing of Sawed Timber. Standard 
dressing shall mean that not more than I inch shall be 
allowed for dressing each surface. For instance, a 12 
by 12 inch timber after being dressed on four sides shall 
measure not less than 11^ by 11| inches. 

STRINGERS. 
Standard Heart Grade. Longleaf Yellow Pine. 

Shall show not less than 85 per cent heart on the girth 
anywhere in the length of the piece; provided, however, 
that if the maximum amount of sap is shown on 
either narrow face of the stringer, the average depth 
of sap shall not exceed | inch. Knots greater than 1| 
inches in diameter shall not be permitted at any sec- 
tion within 4 inches of the edge of the piece; but knots 
shall in no case exceed 4 inches in their largest 
diameter. 

Standard Grade. Longleaf and Shortleaf Yellow 
Pine. Shall be square-cornered, with the exception 
of 1 inch wane on one corner. Knots shall not exceed in 
their largest diameter one-fourth the width of the face 
of the stick in which they occur, and shall in no case 
exceed 4 inches. Ring shakes shall not extend over 
one-eighth of the length of the piece." 

There are also given at length definitions of standard defects, 
including knots, pitch pockets, shakes, wane, red heart, etc., 
for which the reader is referred to the Year-Books and Proceed- 
ings of this Society. 



78 

The committee on grading structural timber, of this Society, 
has been enlarged within the past year and several subcom- 
mittees have been recently formed in anticipation of formulating 
more reliable specifications. 

Interstate Rules for Grading Lumber. 

The Interstate Rules for Yellow Pine Lumber for 1905 

define "Prime Quality, Dimension Sizes," as follows: — 

"All square lumber shall show two-thirds heart 
on two sides, and not less than one-half heart on 
two other sides. Other sizes shall show two-thirds 
heart on face and show heart two-thirds of length on 
edges, excepting when the width exceeds the thickness 
by three inches or over, then it shall show heart on the 
edge for one-half the length." 

Merchantable Inspection. "All sizes under nine inches 
shall show some heart entire length on one side. Sizes 
nine inches and over shall show some heart the entire 
length on two opposite sides," etc. 

The specification for "prime quality" loses most of its force 
when applied to pine of the type shown in Fig. 57. The young 
heartwood has rotted nearly as rapidly as the sapwood. Tim- 
ber of merchantable inspection, in addition to the uncertainty 
of the heartwood mentioned above, has the practical certainty 
of rot in the sapwood if conditions are not most favorable. 
This grade is particularly treacherous with the deep narrow sec- 
tions frequently used for double beams. 

The above specifications all refer chiefly to heart and sap 
and sizes, and have little real relation to strength or dtira- 
bility or to need of treatment, such as kyanizing, to make the 
lumber really worth putting into a building. 

Specifications of Qeorgia=Florida Saw Mill Association. 

The following specifications have been adopted within 
the past year by the Qeorgia=Florida Saw Mill Association 

as a basis for grading structural timber. 

"For timbers and dimension, there must show on 
the cross section between the third and fourth inch 
measured radially from the heart center or pith, not 
less than six annual rings of growth, a greater number 



of which shall show at least one-third summerwood, 
which is the dark portion of the rings of growth. 
Wide ringed material excluded by this rule will be 
acceptable, providing that in the greater number of 
the annual rings the dark ring is hard and in width 
equal to or greater than the adjacent light colored 
ring. In all cases there must be sharp contrast in 
color between the spring and the summerwood. 

For sizes where the center cannot be determined, 
the following will apply: There must show on the cross 
section an average of not less than six annual rings of 
growth, with not less than one-third summerwood, and 
otherwise as provided for in paragraph I." 

Proposed Specifications of Yellow Pine Mfrs. Association. 

The Yellow Pine Manufacturers' Association were considering 
the following before that organization disbanded: — 

"The classification of structural material is a question 
of strength and durability. 

In untreated material this can best be determined 
by its density, as- represented by the proportion of 
summerwood to springwood in the annual growth rings. 

Growth rings are composed of bands of hard, dark, 
resinous summerwood, and lighter, softer, less resinous, 
springwood in each growth ring, and the greater the 
proportion of summerwood, the greater the strength 
and durability of the timber. 

Dense wood shows on cross section an average of 
not less than eight growth rings per inch, measured 
over the third, fourth and fifth inches, on a radial line 
from pith to circumference, containing in the greater 
number of the rings one-quarter or more of summer- 
wood, or, may have an average of six or seven rings as 
above, provided in the greater number of rings one-third 
or more of the ring is summerwood or wider ringed 
material if in the greater number of rings one-half or 
more of the ring is summerwood as above, and must 
show a sharp contrast in color between springwood and 
summerwood." 



80 

These rules just quoted are based on observations of the 
U. S. Forest Products Laboratory, part of which are given 
in Bulletin 108. Both are much in advance of present grading 
methods. 

This bulletin calls attention to the important influence on the 
strength of a beam which the location of defects has. A large 
knot near the center or neutral axis of a beam will affect its 
strength but slightly, while the cross-grain caused by smaller 
knots will decidedly reduce the strength if located on the sides 
where the beam is in greatest tension or compression. A number 
of tests are given showing the effect on the strength, of defects 
so located. It has therefore been suggested that the surface 
of beams be divided into three areas for grading purposes and 
that larger knots be permitted in the central area near the 
neutral axis than in the outer tension and compression areas. 

By similar reasoning, it would be expected that timbers which 
have the lightest part of their wood at the outside and the 
heaviest in the center would have the strength corresponding 
to the lightest wood instead of that corresponding to the average. 

The grain band rule is based on strength and is only indirectly 
connected with durability. Heavy, close grained longleaf pine 
has proved durable in structures, probably because such wood 
is also generally resinous. For the fine grained shortleaf having 
the required percentage of summerwood, which will be admitted 
under these rules, durability is uncertain. 

What is Needed in a Specification. 

The ideal specification is undoubtedly a clear descrip= 
tion of the qualities required. In structural timber these 
are strength and durability. With these qualities defined, 
attributes such as botanical variety, or location of growth, lose 
much of their importance. The limits of strength can be easily 
given, but not easily determined, without destroying the piece 
in question. The density is a sufficiently close index of strength 
for commercial purposes. The percentage of summerwood would 
undoubtedly serve every purpose for describing the required 
material except that in case of dispute this is difficult to measure 
precisely. In order to provide a definite standard, easily used 
or applied, the minimum acceptable density should be given in 
pounds per cubic foot dry. 



81 



From all information thus far available, the percentage of 
rosin is the most reliable index of durability for the Southern 
pines. The dark, greasy appearance of the summerwood will 
be sufficiently reliable for grading purposes under ordinary 
conditions. This is implied, if not clearly stated, in the state- 
ment in the above specifications, "must show a sharp contrast 
in color between springwood and summerwood." In order to 
avoid misunderstandings and to settle disputes, a clear 
statement should be made of the minimum percentage 
of rosin that will be accepted. 

Branding as a Guarantee. 

It has been suggested by Mr. Weiss, Director of the United 
States Forest Products Laboratory, that longleaf pine tim- 
ber should be branded by the manufacturers. This is an excel- 
lent idea. Under present conditions the manufacturers are the 
only people who can positively say whether the timber is long- 
leaf or not, as the standing loblolly, longleaf and shortleaf 
timber exhibits the distinguishing differences in bark, leaves and 
cones, not shown when cut into lumber. See Figures 63, 64 
and 65. 




Figure 63. 
Longleaf pine. 



Figure 64. 
Shortleaf pine. 



Figure 65. 
Loblolly pine. 



82 

After the trees are cut into lumber, it is practically im= 
possible to check grades based upon botanical varieties. 

Branding, without a clearly defined description of the several 
grades of wood, which can be checked by methods within the 
power of the purchaser, will depend entirely for its value upon 
the honesty and carefulness of the lumber manufacturer ; but, 
with well defined physical and chemical specifications, such as 
those in common use with iron and concrete, the branding can 
be checked by the purchaser when necessary and will faciHtate 
inspection on the job. 

True Conservation. 

Much is being written by students of forestry on the closer 
utilization of the forests. This is undoubtedly a commendable 
field of endeavor, but the utilization should be permanent 
and not consist in simply passing the loss along from 
the lumber manufacturer or dealer to the owner of the 
building. 

The use of timber, which, without antiseptic treatment, is not 
durable, in an important structure where it wiU rapidly rot and 
cause a loss of at least double its own value, is not proper 
utilization since it soon results in economic waste of the most 
prodigal sort. 



83 



CHEMICAL TREATMENTS TO PREVENT ROT. 

Antiseptic treatment is the only practicable procedure 
for lumber of doubtful durability, because of its porosity, 
light weight, sap or previous exposure to infection, or 
when it is to be used in a moist atmosphere. 

Much attention has been given to the treatment of railroad 
ties, posts, or other material intended for use near or in contact 
with the earth. But little study has in the past been given to 
the antiseptic treatment of mill timber. The well-known natural 
resistance of good longleaf pine in past 3^ears has been con- 
sidered sufficient to guarantee the permanence of structures. 
This is undoubtedly sound judgment when good quahty, dense, 
resinous longleaf pine is used, as experience in the older mills 
has clearly shown, but the ordinary quality of pine now 
commonly used for heavy mill frames does not have this 
natural resistance. 

The use of this ordinary quality of timber, unsatisfac= 
tory though it be, has become a necessity. With antisep= 
tic treatment and reasonable allowance for the difference 
in strength between light weight and dense timber, the 
quicker growing varieties will fill the requirements of the 
future as satisfactorily as the longleaf Southern pine 
has done in the past; but the use of light, sappy, quick-growing 
varieties of pine, under conditions now found in many kinds of 
factories and other structures, without antiseptic treatment 
has been and will be followed by disaster. 

There is not yet experience enough with factor^^ timbers to 
prove just how great an increase in Hfe will be given by antiseptic 
treatment. Aluch depends on the exposure. Some idea may 
be had by the greater life of the dense "old fashioned" Georgia 
pine as compared with some of the timber received to-day. 
Some idea also may be had from the increase of Hfe given ties 
and telegraph poles by various processes, and by the experience 
with timber kyanized many years ago at Lowell and exposed 
under conditions that invited decav. 



■84 

The increased life of railroad ties due to antiseptic 
treatment, is given by Clyde H. Teesdale^ of the United States 
Forest Products Laboratory, as follows: — 





Untreated 


10 lbs. Creosote 




Hb. 




Years. 


per 


cubic foot. 


Zn 

per 


. Chloride 
cubic foot 


White oak 


8 










Longleaf pine 


7 




20 






Douglas fir 


6 




15 




11 


Spruce 


6 




14 




11 


White pine 


5 




14 




10 


Tamarack 


5 




15 




11 


Hemlock 


5 




15 




11 



The following table gives the increased life of telegraph poles 
in Germany and Austria, after being treated by several preserva- 
tive processes, as given by Dr. Frederick Moll,- from Govern- 
ment records. 

Untreated poles 4.5 years 

Treated with zinc chloride 12.2 " 

Copper sulphate (Germany) 14. 5 " 

Copper sulphate (Austria) 12.3 " 

Bichloride of mercury 16.5 " 

Creosote (15 lbs. cubic foot) 23 . " 

What kind of antiseptic treatment shall be used is an 
important question. Numerous compounds have been pro- 
posed. The problem of treating timber for factory construction 
is different from that of railway ties and posts. Increased fire 
hazard, resistance to paint, and a disagreeable odor are of no 
importance with ties or posts, but are of great importance 
with factory timber. Moreover, the leaching action of rain or 
ground water is important with posts and ties and of no im- 
portance in buildings where the material is protected from the 
weather. For this reason, the numerous creosote and tar com- 
pounds in extensive and successful use with ties are less suited 
to treating factory timber. The metal salts, such as corrosive 
sublimate, are preferable according to all the evidence thus far 
available. 

1. American Lumberman, September 26, 1914. 

2. American Wood Preservers Association, Proceedings 191-4, page 237. 



85 

The fungus=destroying power of various antiseptics has 
been carefully studied by several investigators. The fol- 
lowing table is given by Falck.^ This not only gives the relative 
toxic power of the several materials, but the comparative value. 
The results are derived from laboratory experiments on ger- 
minating spores and fungus grown on various media. This must 
be given due consideration in estimating the practical value of 
the materials as preservatives. More reliable tests are those 
which are carried out over long periods of time under the con- 
ditions of actual service. Toxic materials may be either 
volatilized and removed, or chemically changed and thereby 
made inert, or they may combine with reactive parts of the wood. 

By "inhibition concentration" is meant that strength which 
is just sufficient to destroy the fungus under investigation. 

Inhibition Price per Pound 
Concentration. Multiplied by Inhibi- 

Parts in a tion Concentration. 
Material. Thousand. 

Phenol 1 . .50 

Dinitro-o-cresolate of soda, .05 56 

2:4 dinitrophenolate of soda, .05 10 

Silicon- magnesium fluoride. . 1. 100 

Sodium fluoride .... .^. . . . 1. 75 

Boracic acid 2.' 114 

Corrosive sublimate 1. 520 

Sulphate of copper 10 . 550 

Chloride of zinc 5. ' 215 

Sulphate of iron ■ 20. 280 

Salt 100. 1000 

As a result of his investigations of a large number of different 
proposed toxic materials, Falck recommends the sodium din- 
itrophenolate, which is shown to be the most powerful fungus 
poison in the above list. This chemical is practically unknown 
in this country, and no experience with it as a wood preservative 
is available. Its chemical formula indicates a readily combus- 
tible substance although it is stated that its explosive quaHties 
have been overcome. 



1. Hausschwammforschungen, Vol. 6, page 377: 



86 

Experiments made in the mines of France^ with "Antinon- 
nine" showed it to be much less efficient than creosote as a 
wood preservative. This material is stated to be dinitro- 
cresolate of potassium. From the chemical similarity, it would be 
expected that its action would not be much different from that of 
the dinitrophenolate and cresolate of soda given above. 

Sodium fluoride shows up very favorably in the above 
list. Its low price and high antiseptic value commend it. 
Experience with it as a wood preserver is lacking. It is cer- 
tainly worth trying and it is hoped that in the near future some 
experiments can be made with this material for treating factory 
timber. 

Dean and Downs^ give the toxic value of creosotes from 
laboratory tests as follows: 

Inhibition 

Concentration. 

Parts in a 

thousand. 

A Coal tar creosote No. 1 below 1 

B Coal tar creosote No. 2 1 

C Water gas tar creosote No. 1 4 

D Water gas tar creosote No. 2 3.5 

E Pressed anthracene oil above 8 . 5 

F Sample A minus the phenols 3 

G Sample A minus the phenols & tar bases, 6 

Materials which are in no sense poisonous can resist fungus 
successfully, as in the case of the wood cells filled with water. 
It is probable that the beneficial result from some of the tars 
is caused by their waterproofing qualities. On the other hand, 
well-known bacterial antiseptics may be worse than useless for 
treating wood, as is shown by a building in Italy in which chlor- 
ide of hme was used on the timber.^ The chloride of calcium 
left in the wood cells attracted water and the building was 
quickly destroyed. 

Coal tar compounds are more used for preservative 
treatment of wood than all other materials together. 

They act mechanically and chemically, serving as waterproofing 



1. Preservation des Bois. E. Henry, 1907, page 19. 

2. Antiseptic Tests of Wood Preserving Oils, Dean & Downs, Journal of 
Industrial and Engineering Chemistry, Vol. 5, page 126, 1912. 

3. Atti del Reale Institute Veneto di Scienze Letters ed Atti, 1904, Vol. 
XLIV, Parti 1. 



87 

as well as antiseptics. There has been more or less controversy 
as to the value of carbolic acid, naphthaline and other con- 
stituents.^ 

Most of the tar products used are by-products of the gas 
industry, and it is not a question of the most toxic material, but 
of the most toxic material with reasonable consideration of cost 
and permanence. 

Many proprietary compounds are being sold for timber 
treating. The price is generally high, ranging from fifty 
cents to a dollar a gallon. Coal tar creosote can be bought for 
much less, and, judging from laboratory experiments of the 
U. S. Forest Service,- as well as practical tests in the mines of 
France,^ creosote is fully as serviceable as an antiseptic where 
a coal tar compound is required. 

The following figures are taken from a paper entitled "Tox^ 
icity of Various Wood Preservatives" by C. J. Humphrey and 
Ruth M. Fleming of the U. S. Forest Products Laboratory: 

KiUing Point in parts per 1000. 
Fames Annosus. Fames Pinicola. 
Wood tar (hard wood) . ... 12.5 7.5 

Water, gas, tar creosote. . . 4.5 to 400 

Coal tar, creosote 5.5 2 . 25 

Avenarius carbolineum. ... 52 . 5 3 . 00 

S. P. F. Carbolineum 22.5 

C. A. Wood Preserver .... 10 to 15 

Sodium fluoride 2.5 1.5 

Zinc chloride 5.0 7.5 

It is apparent from these results that the toxic or killing 
power varies considerably with the variety of fungus. This is 
particularly marked with antiseptics of low toxic power, therefore 
the results of experiments, showing moderate toxic power, with 
a given fungus, must be applied with caution to other fungi. 
Preservative materials of higher toxic power show less marked 
variation with different fungi. 



1. Preservation of Timber, Bolton, 1885. 

2. C. J. Humphrey and Ruth M. Fleming. Journal of Industrial and En- 
gineering Chemistry, Vol. 6, page 128, 1914. 

3. Preservation des Bois, E. Henry, 1907. 



88 

The figures given on pages 85, 86 and 87 cannot be directly 
applied to the cost of timber treating processes in terms of 
dollars per thousand feet. They show only the relative quan- 
tities of the several materials required to obtain the same poison- 
ing effect on certain fungi. The second column of figures on 
page 85 introduces the price per pound of the chemical in order 
to get a ratio of comparison; for example, if the corrosive subli- 
mate required for a given penetration effect in an open tank 
treating process costs two dollars per thousand feet of lumber, 
the same antiseptic effect could be obtained with sodium fluoride 
at a cost of about two dollars divided by 520 and multiplied 
by 75, that is, 30 cents. The labor would cost the same in each 
case. If instead of an open tank process, a vacuum process is 
used, in which ten times as much solution is absorbed, the ratio 
still holds, that is, twenty dollars for corrosive sublimate and 
three dollars for sodium fluoride, although the toxic value pound 
for pound of the two chemicals is shown as the same, the dif- 
ference being due to the price per pound. 

Various observations show that liquid oils do not thor= 
oughly waterproof wood and, from all evidence obtainable, 
fungus is able to thrive about the same on oil soaked wood as 
upon wood without oil, if the conditions of humidity are favor- 
able. An example of this is shown in the following photograph, 
which shows the under side of a piece of 3" hemlock plank from 




Figure 66. Rotted 3" Hemlock floor planks. Although 
saturated with paraffine lubricating oil, the fungus continued 
to advance where the moisture was sufficient. 



the floor of a cordage factory, taken from under spinning ma- 
chines, where considerable quantities of moisture were being evap- 
orated, raising the relative humidity locally to near the saturation 
point. Strips of flooring about 4 ft. wide, the entire length of the 
mill, were rotted under these machines, although this floor was 
thoroughly saturated with paraffine lubricating oil, so much so 
that the rotted wood removed dripped oil. 

It is evident that the moisture in wood is to a considerable 
degree independent of the oil which it contains. In other 
words, there is room for both oil and water under certain condi- 
tions. An example of this is wooden casks of linseed oil or 
varnish, which dry up and allow the contents to leak out, if not 
kept in an atmosphere of sufflcient humidity to keep the staves 
swelled tight. It is probable that the liquid state of the oil has 
considerable to do with this action, and that resin or wax will 
prove more efficient as a waterproofing agent. For example, a 
part of this floor which had rotted was repaired several years 
ago with resinous longleaf pine. This is still sound. 

Coagulation of the albuminous compounds of the wood is 
frequentty mentioned in the literature on wood preservation, 
as an important factor. Confusion exists as to the difference 
between simple coagulation by boiling, and combination with 
an antiseptic material. The former action could serve to ster- 
ilize already infected wood. This is one of the valuable results 
of kiln drying, but it in no way prevents later infection. A 
permanent combination of the antiseptic material with the wood 
can serve to prevent later infection. Bolton^ is of the opinion 
that combinations between carbolic acid, or naphthaline, and 
wood albumen are of little importance, as the compound is 
easily broken up by water. He regards carbolic acid of little 
permanent value owing to its volatility. 

Creosoting, etc. 

The disagreeable odor, black, greasy surface and in= 
creased inflammability are objectionable qualities of the 
coal tar antiseptics. In basement floors or rooms with wet 
occupancy, these objectionable qualities may not be prohibitive. 

An oily antiseptic in considerable quantity on wooden ceilings 
can increase the fire hazard in sprinklered mills, as a fire once 

1. Preservation of Timber, Bolton, 1885 



90 

started can travel across the oil-soaked ceiling more rapidly 
than the sprinklers can open, involving large areas. The high 
flash point of the oil makes little difference because a thin film 
on wood, which is a poor conductor of heat, is rapidly heated by 
its own combustion to a sufficiently high temperature to burn 
rapidly. This action is decreased with time as the oil soaks 
deeper into the wood and the more volatile parts disappear. 
This action would be more serious in a building than in the open 
air where the heat would be rapidly carried away with the hot 
gases. 

Burnettizing by use of chloride of zinc is extensively 
used and has given generally satisfactory results for rail= 
road ties. It is understood to be considerably less expensive 
than creosote. There is, however, a suspicion that it may 
reduce the strength of the material. The action may be slow 
but continuous and accelerated by moderately elevated tem- 
peratures. In a report on the preservation of timber by a 
special committee of the American Society of Civil Engineers 
in 1885, it was stated that Burnettized bridge timber, that is, 
timber treated with chloride of zinc, was weakened 10% or 
more.^ It was also stated that railway ties treated with this 
material gave better satisfaction kept away from light and air 
by a covering of earth. 

Chloride of zinc is a well-known solvent of cellulose. It is 
probable that if the timber was not deeply treated or kept at 
a moderate temperature it would do little harm. However, 
with deep penetration or higher temperature, investigation is 
needed as to its effect on the strength of the timber before it is 
recommended for indiscriminate use in the important parts of a 
structure. 

Kyanizing. Kyanizing by use of corrosive sublimate was 
patented in England in 1832. Since then it has been in limited 
but successful use. 

The Locks & Canals Co., which is the Subsidiary Corporation 
owning the water power and is in turn owned by the mills of 
Lowell, Mass., commenced using this process in 1848 and have 
kept careful records of the results. For nearly half a century 
this concern was under the actual management of one of the 
ablest engineers in America, Mr. James B. Francis, who adopted 

1. Transactions American Society of Civil Engineers, 1SS5, page 325. 



91 

Kyanizing after careful investigation and for more than sixty- 
years maintained a small plant for treating such timber as needed 
about the canals or in the mills in places peculiarly subject to 
decay. Spruce was the timber mostly treated. Mr. James 
Francis^ stated that kyanized fence posts were in service in 1891. 
that were set in 1850, It is understood that some of these posts 
are still in service sixty-three years after they were set. Timber 
parts of bridges, where conditions are exceptionally trying, re- 
mained in service thirty-two years. The bridge timber, how- 
ever, was carefully selected and seasoned before treatment, a 
condition which may have somewhat added to the efficiency of 
the antiseptic. 

The only failures of which I have been able to learn are base- 
ment floors where the planking was cut after being treated, 
thereby exposing the untreated center of the plank, for the 
penetration is commonly only about one=quarter of an 
inch. 

The method of treatment employed is to soak the material 
in a cold 1% solution in a masonry, concrete or wooden tank, the 
time of soaking being arbitrarily set at a day an inch plus one, 
that is, for a beam 4'^ x 10", five days, and for one 6" x 10", 
seven days. 

The solution attacks iron and other metals so that it is not 
found practicable to use it in metal tanks. It is claimed that 
the mercury once in the wood enters into chemical combinations 
with its albuminous constituents and becomes insoluble so that 
it cannot be leached out. 

The Berlin Mills Co., an old and favorably known concern, 
has a Kyanizing plant and offers treated timber for sale. 

Several mills have recently treated roof planks with 
corrosive sublimate in their own yards. Wooden and con- 
crete tanks have been used. The concrete has proved most 
satisfactory from cost, tightness and convenience. The absorp- 
tion of solution varies from four or five to forty per cent of the 
weight of the timber, according to the amount of sap wood and 
fungus in the wood, and also the state of seasoning of the timber. 



1. Methods of Preserving Timber in Situations Which Expose It to Decay. 
James B. Francis. New England Cotton Manufacturers Association, Oct., 1891. 



92 



We recommend this process because of the half century 
of successful experience and the ease of application of the 
process and its economy. Experience shows that the well 
known poisonous character of corrosive sublimate when taken 
internally by men or animals can readily be safeguarded, and^ 
so far as I can learn, no sickness or death has ever resulted from 
the practical application of the process. In fact corrosive 
sublimate in very weak solution is one of the most widely used 
antiseptics in hospitals and sick rooms. Only common sense- 
safeguards are needed, such as enclosing the tank and treating 
yard with a close fence, keeping the chemicals under lock and 
key and conspicuous "poison" labels attached to the tank. 
Preferably the treated lumber should be branded "Kyanized"' 
with hot, thin edge iron letters an inch high. 

Kyanizing has no objectionable effect on paint subsequently 
appHed. 



93 
A GREAT NEED FOR BETTER DATA. 

On pages 85, 86 and 87, several preservatives have been listed, 
which promise well, but with most of them we lack experience 
in the practical application and as to the strength after ten or 
forty years, and as to their effect on paints, etc. 

There is now the same need for experiments on the natural 
resistance and the effect of various kinds of preservation upon 
full sized beams and columns of commercially available 
timbers, under carefully controlled conditions of humidity and 
heat, and with exposure to known varieties of fungus, that 
existed a few years ago with reference to the strength of structural 
timber. 

It is even less logical to generalize on the power of resistance 
to fungus of the several varieties of timber and upon the efficiency 
of timber treatments from laboratory experiments on small 
pieces in flasks, or small fungus pits where humidity, temperature 
and fungus are not carefully controlled, than it is to calculate 
the strength of large beams from tests on small specimens. 

^Moreover, experiments under practical service conditions do 
not give all the information desirable, for it has been shown 
that variations in atmospheric humidity, imperceptible without 
the use of carefulh^ arranged measuring instruments, are sufficient 
to account for the wide differences observed in the destruction 
caused bv common wood destroving fungi. 



94 



KYANIZINQ TIMBER IN THE MILL YARD. 

nullify 





Figure 67. Southern pine heartwood roof planks for a 

PAPER MILL, BEING TREATED IN A SHALLOW CONCRETE TANK, 
AT A COST OF ABOUT THREE DOLLARS PER THOUSAND INCLUDING 
THE COST OF THE TANK. 




Figure 68. 4" spruce planks and Southern pine beAxMS for 
a weave shed roof being treated in a wooden tank. 





1 


1 ^ -^^^^^'^^i!^^«C5M^H 


iBHP^ *^-.' '-^•;i&llt>m r-""^"' '-'^^^^^^^^BfcBiMBI 



Figure 69. 2" Southern pine containing micii sapwood, 
being treated for a weave shed roof. absorption 
varies from 5% to 35% of solution by weight. 



95 

PENETRATION OF ANTISEPTICS. 

The penetration of antiseptics has been increased by 
the use of vacuum and pressure processes, applied in 
closed tanks. Alternate heating and cooling also increases the 
penetration. This process is sometimes carried out by dipping 
the timber first into a tank of hot material and then into cold, 
or by boiling it for a time and then allowing it to cool. By 
suitable manipulation, in addition to obtaining considerable 
depth of penetration, the wood cells can be left full or nearly 
empty, as desired. This method is based on the expansion and 
contraction of the air in the cells. A heating process might be 
used with corrosive sublimate to increase the penetration where 
this is necessary. It is probable that the present method with 
the cold bath is sufficient for mill lumber not subject to exces- 
sive moisture. 

The relative penetration of the different common woods 
by oily antiseptics is given by C. H. Teesdale.^ The depth 
of penetration is least with the first wood mentioned, and 
increases in the order given. 

1 Douglas fir heartwood 7 Loblolly pine heartwood 

2 White spruce heartwood 8 White spruce sapwood 

3 Eastern hemlock 9 Douglas fir sapwood 

4 Western hemlock 10 Longleaf pine sapwood 

5 Shortleaf pine heartwood 11 Shortleaf pine sapwood 

6 Longleaf pine heartwood 12 Loblolly pine sapwood 

Miss Gerry2 shows that the tyloses, which are a sack-like 
formation in the wood cells, are a factor in the durability of 
woods as well as the penetration of antiseptics. This action is 
attributed to the obstruction which these growths offer to the 
advance of the fungus as well as to the penetration of air and 
water. Durable woods generally have tyloses and they are 
especially effective in woods which have been dried. 

Brush treatments of timber with antiseptic solutions have 
some value in retarding the progress of fungus as is shown by a 
recent Forest Service publication.^ A recent experience 
in a weave shed basement shows that it is not safe to depend on 
brush treatment of timber already infected, if the antiseptic 
material depends chiefly for its preservative effect on its water- 
proofing qualities. 

1. Bulletin 101, Department of Agriculture, Forest Service, 1914. 

2. Journal of Agricultural Research, Vol. 1, page 462. 

3. U. S. Dept. of Agriculture, Forest Service Circular 198, Sept. 1912. 



96 



COST OF TIMBER TREATING. 



The added cost of antiseptic treatment is not prohib= 
itive. The price quoted by treating companies varies from 
$S to $15 per 1,000 feet board measure. 

The cost of treating with corrosive sublimate at certain 
factories insured by these companies has averaged about 
three dollars per thousand feet, B. M., for reasonably good 
timber. 

It is necessary to see that the material is not water-soaked, 
frozen, or already deeply infected with living fungus when treated. 
The ideal time and place of treatment is immediately after 
sawing at the saw-mill, as much of the lumber is undoubtedly 
infected long before it reaches its final destination. See Fig- 
ure 58. 




Figure 70. Fruiting lachrymans fungus on the frame of a 

LUMBER SHED AT A SOUTHERN SAW-MILL. 

A plan which commends itself is to give the lumber a 
light treatment at the saw-mill with an antiseptic, such as sodium 
fluoride, which, being less poisonous than corrosive sublimate, 
would not prejudice it for common uses; then, after it is cut 
to final shape, to give it a second treatment suited to the condi- 
tions under which it is to be used. Indeed, corrosive sublimate 
applied in the small percentages required for timber preservation 
is very seldom objectionable. 



97 

SUMMARY. 

In conclusion, the following suggestions are made, based on 
observations and experience thus far: — 

In building a paper mill or weaving mill, in which the atmos- 
pheric humidity will be high, antiseptic treatment is well 
worth its cost with any timbers now practicably obtainable. 
A creosote treatment of about twelve pounds per cubic foot is 
as good as anything in practical use for moist locations where 
the fire hazard is negligible and the lumber is to be near or in 
contact with the earth, but concrete is generally preferable to 
timber in such locations. 

A form of construction for one story and basement paper 
mills and weave sheds which has many advantages, is a con- 
crete floor, protected steel columns, and a heavy plank roof. 
When a concrete roof is used in a cold climate and there is 
high inside humidities, it is necessary to provide efficient insulat- 
ing material on the outside to prevent the rapid conducting away 
of heat and consequent condensation. A dripping roof is highly 
objectionable for most occupancies. A thick wooden roof is 
the best heat insulator that can be had for the price. There 
are conditions under which it wiU. be worth while, with this end 
in view, to increase the thickness of the roof to four or five 
inches. For securing durability in such thick roofs, it 
will be absolutely necessary to use material that is 
thoroughly fungus=proofed with suitable antiseptics. 
The roof should also be made sufficiently tight to prevent 
moisture laden air from passing through cracks against the cold 
outer covering where the condensed moisture will keep the 
planks water-soaked. 

Thin plank roofs have been used in a few cases with fibrous 
insulating material on top, which can absorb water. The highly 
humidified air inside passed through cracks in the roof boards 
and saturated the insulating material with water, thereby 
destroying its insulating power and increasing the tendency 
to rot in the roof planks. 

For roof planks over rooms where humidit}^ is high, treat- 
ment with corrosive sublimate is undoubtedly worth its small 
cost. No experimental data is available as to the increased 
life to be expected from this treatment; but, judging from 



experience with other uses to which kyanized material has 
been put, the hfe should be greatly lengthened. 

For use on a roof where insulation is the first consideration, 
the planks being made extra thick to secure this end, low-grade 
material can be used if it is sufficiently resistant to rot; knots, 
shakes or resin pockets are of little importance if the material 
is thoroughly rot-proofed. 

For ordinary dry mills where the average humidity is 50% or 
less, it may be possible to obtain Southern pine with sufficient 
natural resistance to withstand fungus, untreated, if sufficient 
care is given to its selection. According to present usage, the 
words "longleaf" and "shortleaf" in connection with Southern 
pine lumber are meaningless. Heartwood in all varieties is 
necessary for durability. 



99 



The following suggestions for specifications are offered 
for use when Southern pine timber of an excellent quality 
is required. 

The following paragraphs will serve to eliminate much of the 
shortleaf, loblolly, and poorer qualities of longleaf, as well as to 
prevent misunderstandings and to facilitate the settlement of 
disputes if added to the specifications describing the required 
limitations of grain bands per inch and percentage of summer- 
wood, as adopted bj^ the Georgia-Florida Saw Mill Association, 
given on page 78, and the common limitations of knots, wind- 
shakes, wane, etc. 

Specifications proposed. 

DENSITY. No part of the material shall have a den= 
sity of less than thirty pounds per cubic foot when tested 
by boring smooth holes one inch in diameter and two 
inches deep in the ends of the stick, drying to constant 
weight at 212° F. and weighing the borings and com= 
puting the density from the volume of the hole. 

ROSIN. None of the heartwood shall show less than 
4 per cent of rosin by weight when borings are taken with a 
one inch bit with a hole two inches deep dried to constant 
weight at 212° F., and extracted with benzole, the ex= 
tracted rosin evaporated until it is not soft or sticky 
when touched with the finger at 70° F. 

HEARTWOOD. Heartwood shall show in all four faces 
of every stick, and sapwood shall not extend more than 
two inches from the corner at any place, measured perpen= 
dicularly to the corner across the face. 

DEFECTS. No timber with knots greater than one 
inch in diameter, or rot or injurious shakes will be 
accepted. 

BRANDING. Longleaf pine sold under this specifica= 
tion shall be branded with the letters "F. M.," with the 



100 

name of the lumber manufacturer, the location of the 
saw-mill from which it comes, and the date of sawing, 
in letters at least one inch high. 

The above specifications will require selected longleaf pine 
from the butts of trees and will undoubtedly command a con- 
siderably higher price than "commercial longleaf pine." It will 
also be worth a higher price. It is a "grade" not known to 
the lumber trade at present. There is some of it in the South, 
but, by methods now in use, it is mixed with poorer timber and 
its good qualities are lost, as it is not the average, but the poor- 
est that characterizes the lot. 

The place of shipment is no guarantee of the quality of 
the stock, as in most places where longleaf pine is growing 
there is also shortleaf and loblolly. 

In some places, the proportion of longleaf is greater than in 
others. The care and good reputation of the lumber manu- 
facturer is of more importance in assuring good material than 
the place of shipment. 

Spruce and hemlock are undoubtedly much less resistant to 
common timber destroying fungi than good quality Southern 
pine heartwood, and it is a safe rule to avoid the use of these 
woods without antiseptic treatment in any except the dryest 
locations. 

New lumber frequently contains living fungi in a latent form 
which is difficult to detect. This difficulty is increased by the 
common practice at many lumber yards of planing the stock 
just before it is delivered. The only outward manifestation 
of fungus in the wood is frequently an inconspicuous brownish 
tinge. Nearly every lumber pile on careful examination will 
show a considerable proportion of fungus-infected sticks. In 
some cases these sticks contain tree fungi that are already dead 
and harmless. Living plants often start growing in the lumber 
pile, particularly if the weather is damp, showing lacelike growths 
between the sticks when the pile is taken down. Lumber 
showing such growths had best be given an antiseptic treatment 
if the conditions under which it is to be used are at all moist. 

In several cases, serious rotting has been caused by timber 
which was water-soaked by being left uncovered during a long 



101 

season of rainy weather, and covered in without provision 
for drying. When it is necessary to use such water-soaked tim- 
ber, it will be well worth while to hasten the drying as much as 
possible by use of the heating system. 

Kyanizing can be conveniently done on the job by construct- 
ing a tank of concrete or plank of such shape that the material 
can be packed into it with the least possible voids. It should be 
weighted or held down with bolts so that it cannot float when 
the solution is added. This should consist of corrosive sub- 
limate dissolved in water, one pound to twelve gallons of water. 
The lumber should soak in this solution for a week. The absorp- 
tion will vary according to the quality and variety of the lumber 
from two or three per cent to forty per cent. Care must be 
used in handling the corrosive sublimate as it is very poisonous 
if taken internally. 

Heat Treatment. 

When there is any suspicion of dry rot infection in a 
building, heating from time to time to 115° F., for a day 
or two by use of the steam heating coils, is well worth its 
small cost for arresting the progress of a lachrymans or 
Coniophora infection.. In a new building, it is particularly 
useful as the heat not only arrests these fungi, but assists in 
drying the timber, and thereby kills other fungi. 

Drying a moist basement will arrest many of the common 
fungi that require about 100% atmospheric saturation. This 
can sometimes be accomplished better by a combination of heat 
and ventilation than by ventilation alone, as the heat reduces 
the percentage saturation where there is no water supply to 
keep it up by further evaporation. It is frequently difficult 
to get a circulation of air in a large basement without fans or 
other mechanical means. In some cases, air has been taken 
from a basement, which was giving trouble by rotting, for 
humidifying the mill, thus getting a return for the power re- 
quired for driving the fan. 

In an infected building, the fungus spores would be so 
generally distributed that the few brought up with the air 
currents would add little to the chance of infection of the upper 
parts of the building, which are drier, and therefore the possi- 
biHty of the spread of the fungus from this source is remote. 



102 

One pound of corrosive sublimate dissolved in twelve gallons 
of wood alcohol has been used with apparent success on several 
occasions for local or surface fungus infections. In some cases, 
this material has been injected into small holes bored in large 
beams; and, in others, it has been applied to the surface with 
whitewash brushes. 

The additional cost of the alcohol solvent is only worth while 
under exceptional circumstances, such as timber already in place 
in a moist location, or when economy of time is imperative. 

F. J. HOXIE. 



103 



INDEX 

ABSTRACT 2 

RECENT PROGRESS 4 

EXTENT OF THE DESTRUCTION 6 

The loss to Mutual Mills from rotting timber is many 

thousands of dollars a year 6 

ROT AND FIRE HAZARD 11 

Partly rotten wood ignites much more easily than sound 

wood 11 

INCREASED COMBUSTIBILITY OF WOOD AF= 

FECTED BY DRY ROT 13 

SUGGESTIONS FOR EXAMINING AN INFECTED 

MILL 14 

HOW WOOD ROTS 17 

COMMON TIMBER=DESTROYING FUNGI 18 

There are but few common or popular names for fungi 18 

Fruiting fungi can be easily identified 20 

The dry rot disease is widely distributed in this country 20 
The name Polyporus family has been used to include 

broadly any of the pore fungi 21 
In many cases owing to the absence of fruiting plants the 

fungus causing the destruction cannot be determined 22 

MICROSCOPIC APPEARANCE 23 

RAPID PROGRESS OF DRY ROT 24 

In most cases the rotting found has taken place rapidly 24 

EFFECT OF HUMIDITY ON THE PROGRESS OF 

ROT 25 

Average relative humidity of a building heated to 60° F. 25 
The relative humidity at any temperature is the percent- 
age which the humidity found bears to that required 

for saturation 26 



104 

DRY ROT AND DAMP ROT 28 

Most rot in mill timbers is caused by two groups of fungus, 
one thrives in dampness, the other in air relatively 
much drier 28 

LOCAL DIFFERENCES IN EXPOSURE TO MOISTURE 30 

The relative humidity of air in a room or basement some- 
times is very different in places only a few feet apart 30 
Dry and wet are only relative terms 31 
Certain processes of manufacture require the atmospheric 
humidity to be regulated within narrow limits 31 

WETNESS AND DRYNESS BOTH PREVENT ROT 33 

Wood of great antiquity has been found buried in clay in 

a perfect state of preservation 33 

The weaving rooms of Cotton Mills are frequently main- 
tained at a saturation of moisture of 70% to 80% dur- 
ing working hours 34 
Limits of dampness required for growth of dry rot fungus 34 
A possible source of moisture for supplying the require- 
ments of a fungus growing inside a large beam is the 
decomposition of the wood itself 34 
Ventilation not always a cure 35 
Paint sometimes retards, sometimes accelerates rotting 35 
The conditions for germination and growth of Merulius 

lachrymans have been mysterious 36 

Long life of dormant fungi 36 

Dry rot fungi have two methods of reproduction and can 

remain a long time in a resting state 36 

How the dry rot disease is spread 37 

HEAT AND DRYING ARE USEFUL IN STOPPING 

ROT 38 

Often an infected building can be sterilized by skilful use 
of its heating system 38 

Heat as a means of destroying lachrymans and coniophora 
in mill beams was tried 38 

HOLES IN COLUMNS AND DOUBLE BEAMS WILL 

NOT PREVENT ROT 41 

One of the reasons for bored columns and double beams 
has been to prevent dry rot 41 



105 

SLOW BURNING CONSTRUCTION 44 

Laminated floor 45 

VARIETIES OF TIMBER AVAILABLE 47 

Varieties of timber available for mill construction are 
fewer than those available for railroad ties 47 

It is a significant fact that much of the best longleaf pine 
timber produced in the South is being shipped to 
Europe 47 

COMMON VARIETIES OF SOUTHERN PINE 48 

There is much confusion in local names 48 

The positive identification of longleaf pine lumber is 

difficult or impossible 48 

SOUTHERN PINE AVAILABLE 56 

This shows clearly the need of a system of grading by 
which the heavy resinous material can be separated 57 

The present specifications for longleaf pine of the American 
Society for Testing Materials opens the way to such 
practices by giving a double meaning to the name long- 
leaf pine 58 

ROSIN AS A CAUSE OF RESISTANCE OF WOOD TO 

FUNGI 59 

The causes of natural resistance to fungi in wood are ob- 
scure and have been investigated but little 59 

Heartwood is generally more resistant to fungi than sap- 
wood 59 

The preservative power of rosin is frequently mentioned 
as a matter of general observation 59 

The inverse ratio of the loss of weight to the percentage of 
rosin is in as close agreement as could be expected 60 

In some of the pines there is an abrupt increase in the 
rosin content at the heart line 61 

The longleaf pine heartwood shows a wide variation in 
the rosin content 67 

Under the present system of grading and selection of timber 
the only guarantee of durabiHty is the proportion of 
heartwood 67 

The percentage of rosin in the sound centers of rotted 
beams taken from a mill was determined in order to get 
an idea of the amount at which the fungus stopped 68 



106 

It is apparent that the limiting amount of rosin which is 
just sufficient to stop fungus is in the neighborhood 
of 3% 68 

DURABILITY AND PHOTOGRAPHIC ACTIVITY 71 

The resistance of wood to decay does not depend upon 
any one factor alone 71 

Most woods after being exposed to strong light will act 
upon a photographic plate in the dark 71 

The woods which are photographically active are also 
generally resistant to fungus, but this is generally 
not a universal law 71 

DENSITY AS AN INDEX OF STRENGTH 73 

Light wood is simply wood without much wood in it 73 
The proportion between spring and summerwood has 

been suggested as a criterion for grading timber 73 

DENSITY HAS BEEN SHOWN TO BE A RELIABLE 

INDEX OF STRENGTH OF TIMBER 75 

SPECIFICATIONS FOR STRUCTURAL TIMBER 76 

The specification which has been adopted by the American 

Society for Testing Materials 76 

The Interstate Rules for yellow pine lumber 78 

The following specifications have been adopted within 
the past year by the Georgia-Florida Saw Mill Asso- 
ciation 78 

PROPOSED SPECIFICATIONS OF YELLOW PINE 

MANUFACTURERS ASSOCIATION 79 

These rules are based on observations of the U. S. For- 
est Products Laboratory 80 

The ideal specification is undoubtedly a clear description 
of the quaHties desired 80 

Branding as a guarantee 81 

After the trees are cut into lumber it is practically im- 
possible to check grades based upon botanical varieties 82 

Much is being written by students of Forestry on the 
closer utilization of the forest 82 



107 

CHEMICAL TREATMENTS TO PREVENT ROT 83 

Antiseptic treatment is the only practicable procedure 
with lumber of doubtful durability or when it is used 
in a moist atmosphere 83 

The increased life of railroad ties due to antiseptic treat- 
ments 84 

What antiseptic treatment shall be used is an important 
question 84 

The fimgus destroying power of various antiseptics has been 
carefully studied by several investigators 85 

Sodium fluoride shows up very favorably in the above list 86 

Coal tar compounds are more used for preservative treat- 
ment of wood than of other materials together 86 

Many proprietary compounds are being sold for timber 
treating 87 

"Toxicity of various wood preservatives" 87 

Liquid oils do not waterproof wood 88 

The disagreeable odor, black greas}^ surface and increased 
inflammability are objectionable qualities of the coal 
tar antiseptics 89 

Burnettizing by use of chloride of zinc is extensively 
used and has given generally satisfactory results for 
railroad ties 90 

Kyanizing by use of corrosive sublimate 90 

Several mills have recently treated roof planks with cor- 
rosive sublimate 91 

A GREAT NEED FOR BETTER DATA 93 

Brush treatments of timber 95 

PENETRATION OF ANTISEPTICS 95 

The penetration of antiseptics has been increased b}^ the 
use of vacuum and pressure processes 95 

The relative penetration of the different common woods 
by antiseptic solutions 95 

THE COST OF TIMBER TREATING 96 

The added cost of antiseptic treatment is not prohibitive 96 

SUMMARY 97 

Specifications proposed 99 

Heat treatment for emergency 101 



LIBRARY OF CONGRESS 



THE ASSOCIATED I 

FIRE INSURANC_\?>.! Jii.^!L? 




1 MANUFACTURERS MUTUAL F. INS. CO., Providence^ 

2 RHODE ISLAND MUTUAL F. INS. CO., PrOVt'deUCe, 

3 BOSTON MFRS. MUTUAL F. INS. CO.,; BoStOTt, 

4 firemen's mutual INS. CO., Providence, 

5 state mutual f. ins. CO., Providence, 

6 WORCESTER MFRS. MUTUAL INS. CO., Worcester, 

7 ARKWRIGHT MUTUAL F. INS. CO., Boston, 

8 BLACKSTONE MUTUAL F. INS. CO., PrOVldeUCe, 

9 FALL RIVER MFRS. MUTUAL INS. CO., Fall River, 

10 MECHANICS MUTUAL F. INS. CO., Providence, 

11 WHAT CHEER MUTUAL F. INS. CO., Providence, 

12 ENTERPRISE MUTUAL F. INS. CO., Providence, 

13 MERCHANTS MUTUAL F. INS. CO., Providence, 

14 HOPE MUTUAL F. INS. CO., Provtdence, 

15 COTTON AND WOOLEN MFRS. M. I. CO., Boston, 

16 AMERICAN MUTUAL F. INS. CO., Provtdence , 

17 PHILADELPHIA MFRS. M. F. INS. CO., Philadelphia, 

18 RUBBER MFRS. MUTUAL INS. CO., BostOH, 

19 PAPER MILL MUTUAL INS. CO., Boston, 



JOHN R. FREEMAN, PrCS. 
JOHN R. FREEMAN, PreS. 

J. P. GRAY, Pres. 
F. w. MOSES, Pres. 

JOHN R. FREEMAN, PreS. 

w. E. BUCK, Pres. 
R. w. TOPPAN, Pres. 
WM. B. McBEE, Pres. 
c. s. WARING, Pres. 

JOHN R. FREEMAN, PreS. 
FRANK L. PIERCE, PrCS. 
JOHN R. FREEMAN, PreS. 

WM. B. MCBEE, Pres. 

FRANK L. PIERCE, PrCS. 

BENJ. TAFT, SeC. 

JOHN R. FREEMAN, PreS. 

E. I. ATLEE, Pres. 

BENJ. TAFT, SeC. 

R. w. TOPPAN, Pres. 



The Factory Mutual Fire Insurance Companies were originated 
eighty years ago, by certain prominent manufacturers of New Eng- 
land, for the purpose of lessening fire losses and providing insur- 
ance at actual cost. They confine their business mostly to large 
isolated manufacturing properties. They have improved the con- 
struction of buildings, introduced better fire protection, and each 
risk is subject to expert inspection at least four times per year. 
They insist upon "good housekeeping," complete automatic sprin- 
kler protection, special fire pumps, ample water supply from at 
least two independent sources, and private watchmen. 

These methods have resulted in preventing interruption of busi- 
ness by fire, and enabled the Mutual Companies to return to policy 
holders a large proportion of their premiums which otherwise would 
have been used in payment of heavy fire losses. 

Unless there is more than $75,000 at risk as a base for carrying 
the cost of inspection and engineering service, these Companies 
seldom can afford to take the insurance. 



